Same Name?!--Guy

Guy is a bit odd. Most people today consider it a slang term rather than a name, and that's not completely unreasonable, since it's probably one of the oldest bits of slang in use today--coined in the mid 1800s! Guy was a name long before that, most famously borne by Guy Fawkes, who tried to blow up Parliament in 1605. It's also thanks to him that guy is now a term for "man"--his tale was romanticized in a popular book, and guy entered general terminology meaning "shabby man", later expanded to any male.
Despite this, Guy remained in common use for quite some time, only dropping off the US charts 5 years ago.

And for such a short name, it has a surprising amount of variation from language to language. This is partially because its original form sounded almost identical to a Latin name, Vitus, and where the two languages overlapped, they were treated as the same name. Consequently, it's difficult to separate which modern form evolved from Vitus, and which from Wido.

Original Germanic form: Wido (VEE-doh)
Modern French form: Guy (GEE)

Other forms:

• Guido (GEE-doh)--German
• Guido (GWEE-doh)--Italian
• Gvidas (GVEE-dahs)--Lithuanian
• Veit (FITE)--German
• Vid (VEED)--Croatian, Slovene. Feminine is Vida.
• Wide (WEE-deh)--Frisian
• Wit (VEET)--Polish