bell-boy n.

"hollow metallic instrument which rings when struck," Old English belle, which has cognates in Middle Dutch belle, Middle Low German belle but is not found elsewhere in Germanic (except as a borrowing); perhaps from an imitative PIE root *bhel- "to sound, roar" (compare Old English bellan "to roar," and see bellow).

As a division of daily time aboard a ship, by 1804, from its being marked by bells struck every half hour. The statistical bell curve is by 1920, said to have been coined 1870s in French. Of glasses in the shape of a bell from 1640s. Bell pepper is from 1707, also so called for its shape. Bell, book, and candle is a reference to a form of excommunication (the bells were rung out of order and all together to signify the loss of grace and order in the soul of the excommunicated).

To ring a bell "awaken a memory" (1934) is perhaps a reference to Pavlovian experiments; it also was a signal to summon a servant (1782).

mid-13c., boie "servant, commoner, knave" (generally young and male); c. 1300, "rascal, ruffian, knave; urchin," mid-14c. as "male child before puberty" (possibly extended from the "urchin" sense). A word of unknown origin.

Possibly from Old French embuie "one fettered," from Vulgar Latin *imboiare, from Latin boia "leg iron, yoke, leather collar," from Greek boeiai dorai "ox hides." (Words for "boy" double as "servant, attendant" across the Indo-European map — compare Italian ragazzo, French garçon, Greek pais, Middle English knave, Old Church Slavonic otroku — and often it is difficult to say which meaning came first.)

But it also appears to be identical with East Frisian boi "young gentleman," and perhaps with Dutch boef "knave," from Middle Dutch boeve, perhaps from Middle Low German buobe. This suggests a gradational relationship to babe. Another conjecture:

In Old English, only the proper name Boia has been recorded. ME boi meant 'churl, servant' and (rarely) 'devil.' In texts, the meaning 'male child' does not antedate 1400. ModE boy looks like a semantic blend of an onomatopoeic word for an evil spirit (*boi) and a baby word for 'brother' (*bo). [Liberman] 

Used slightingly of young men in Middle English, also in familiar or contemptuous use of criminal toughs or men in the armed services. In some local uses "a man," without reference to age (OED lists "in Cornwall, in Ireland, in the far West of the U.S."). The meaning "male negro slave or Asian personal servant of any age" attested from c. 1600.

Extended form boyo is attested from 1870. Emphatic exclamation oh, boy is attested by 1917. Boy-meets-girl "typical of a conventional romance" is from 1945; the phrase itself is from 1934 as a dramatic formula. Boy-crazy "eager to associate with males" is from 1923.

A noticable number of the modern words for 'boy', 'girl', and 'child' were originally colloquial nicknames, derogatory or whimsical, in part endearing, and finally commonplace. These, as is natural, are of the most diverse, and in part obscure, origin. [Buck]