Boy

Boy \boi\ , noun;
1. A male child, from birth to full growth, especially one less than 18 years of age
2. Informal: A grown man, especially when referred to familiarly
3. Military personnel, especially combat soldiers
4. Disparaging and offensive: A man considered by the speaker to be inferior in race, nationality, or occupational status

My big 20 week ultrasound was today...it's a boy!

Boy dates to the mid-13th century as boie ("servant, commoner, knave, boy"). Where exactly it came from is uncertain, but here are a few theories:
From Old French embuie ("one fettered"), which comes from Vulgar Latin *imboiare from Latin boia ("leg iron, yoke, leather collar"), which is taken from Greek boeiai dorai ("ox hides").
Related to East Frisian boi ("young gentleman")
Related to Dutch boef ("knave") from Middle Dutch boeve, which is possibly from Middle Late German buobe. This would suggest a connection with babe.
A semantic blend of *boi ("evil spirit") and *bo (baby word for "brother")

There was a name Boia in Old English, but nothing that's obviously linked to Middle English boi. The definition "male child" does not appear until the early 15th century. Using boy as a disparaging term for young men goes back to Middle English. The definition "male negro slave or Asian personal servant of any age" is attested from the 1600's, though many Indo-European languages use their word for "boy" in this way and have for a long time.