GUARANTEED WARRANTY

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!