Day

[tkowal]

I was surprised not to see this extremely common English word, related to Tag (German) and dag (most other Germanic languages). According to Etymoline, its source is Proto-Germanic *dages-, for which there are two possible very different PIE roots: *agh- (a day) and *dhegh- (to burn). The second alternative appears in the Word History of Foment.

Another surprise is that apparently similar Latin dies (Spanish día, Portuguese dia) comes from a very different PIE root: *dyeu-. Slavic languages (Russian den', Polish dzień) share the same source.

[Slava]

Taken up and treated here.