noun
son (of others); young master; boy
Honorific term used to refer to someone else's son, especially a young boy from a respectable family. Often used by older speakers or in service contexts.
お宅のお坊ちゃんはおいくつですか。
How old is your son?
お坊ちゃん、お菓子をどうぞ。
Here, young master, have some sweets.
noun
sheltered young man; naive rich boy
Used somewhat ironically or critically to describe a young man from a wealthy family who is inexperienced or naive about the real world.
彼は苦労を知らない、いわゆるお坊ちゃんだ。
He's what you'd call a sheltered rich boy who doesn't know hardship.
息子さん is a more neutral and common honorific term for 'son', while お坊ちゃん carries a nuance of a young, perhaps pampered boy from a good family.
Formed from the honorific prefix お, the noun 坊 (boy, son), and the diminutive suffix ちゃん. The variant with っちゃん reflects colloquial gemination.