Back in Old and Middle English, the word I had many different spellings, including ic, icc, ich, ikh, and i. You'll notice all those are lowercase; the capitalization started in the fourteenth century, first showing up around the time of Chaucer's Canterbury Tales. It's actually very unusual to have the first person singular pronoun be majuscule - English is the only language that does it - but linguists theorize that it emerged when i became one letter to stress that it was not some kind of typographic error. Ic/icc/ich/ikh comes from Proto-Germanic ek, and that is reconstructed to the Proto-Indo-European root eg, which also meant "I". Going further, there's a New York Times article about this that raises some interesting points: how might the capitalized "I" affected the development of English speakers? How might increased use of lowercase i on the Internet change the use of the word? Why didn't this happen with other words? Just some interesting food for thought.

The word galore was first used in a 1675 diary entry of an Anglican clergyman, when it was spelled gallore. After that, several other spellings, such as gillore, galloure, gilore, gelore, and golore, were attested, with the modern form becoming the norm sometime in the nineteenth century.  The term comes from the Irish phrase go leor, which translates to "sufficiently", "enough", or "plenty". The go part of that traces to Old Irish co, meaning "with" (this was often added to make adjectives from other parts of speech), and that, through Proto-Celtic, derives from the Proto-Indo-European reconstruction kom, "along". Leor, which also meant "enough", is from Old Irish lour, Proto-Celtic lawaros, and ultimately Proto-Indo-European lehw, meaning "benefit". Literary usage of the word galore​ peaked in 2009.

A boustrophedon script is a writing style that is bi-directional, with every other line reversed or mirrored (so while English is read left to right, a boustrophedon would go left to right, then right to left, then repeat). The word was borrowed in 1783 to describe a type of boustrophedon used in Ancient Greece, unsurprisingly from the Ancient Greek language, where it meant "turning as an ox is plowing". That's composed of bous, meaning "ox" (from Proto-Indo-European gwos, "cattle"), strophe, meaning "turning" (from Proto-Indo-European streb, "to wind", and the adverbial suffix -edon, which translates to something along the lines of "in the manner of". Literary usage of the word boustrophedon peaked in 1886, and has recently been on a downward trend.

There's a particularly interesting sound change that occurred from Proto-Germanic into Romance languages that crops up a decent amount in English. Where the language originally had a w sound at the start of words, the consonant shifted into the velar stop g, and a u was inserted after it to differentiate it from the "soft" g. English often borrowed these words, while simultaneously keeping the w- words from Germanic, resulting in some cool pairings. Here are some examples of this:

• Ward and guard both come from Proto-Germanic warduz, also meaning "guard", but guard was borrowed through Old and Middle French
• Warranty and guarantee both trace to Proto-Germanic warjan, "to ward off".
• English war and Spanish guerra derive from werro, meaning "confusion" or "disarray"
  
• The French name Guillaume is a long-lost relative of William
  
• Wasp and its French counterpart, guepe, both come from Proto-Germanic waspo

Anyway, I think that's really awesome!

The word calumny, meaning "slanderous statement", was first used in English around the 1560s and partially popularized when Shakespeare used it in Hamlet. It was borrowed from the Old French word calomnie (with the same meaning), and that was taken in the 1400s from Latin calumnia, "trickery" (also the etymon of the word challenge, on the notion of "false accusation" developing into "accusation" and eventually "confrontation"). The origin of that is calvi, meaning "to deceive", and calvi, based on cognates in Greek and Germanic languages, has been tentatively reconstructed to a Proto-Indo-European root sounding like kehl and having something to do with betrayal or lying. According to Google NGrams, literary usage of the word calumny peaked in 1796 and has been declining since.

The words terrible and terrific are related! Terrible​ was borrowed in the fifteenth century from Old French, and the Old French word was borrowed in the twelfth century from Latin terribilis, meaning "frightful". That comes from the verb terrere, which (much like its other descendant terrify) meant "to fill with fear" and derives from the Proto-Indo-European reconstruction ter, "weak". Terrific also traces to terrere, by means of Latin terrificus, which was pretty much the same as terribilis. Until the late seventeenth century, terrific meant "frightening" as well, but people started using it as an adjective for "great" (sort of like how we can now say that shirt looks terribly good on you). Eventually, the old definition was lost and it took on grander, even more positive connotations, giving us the curious contrast we see today.