σπέρα, compare with latin vesper, both from https://en.wiktionary.org/wiki/Reconstruction:Proto-Indo-European/wek(%CA%B7)speros
French vespéral : of the evening
The sentence "Good evening boy" doesn't seem quite right to me, even though it is the literal translation. I think "Good evening young man" conveys the same sense, while being more polite. In my opinion, it should be an accepted translation.