"gigantic statue," late 14c., from Latin colossus "a statue larger than life," from Greek kolossos "gigantic statue," which is of unknown origin. The Greek word was used by Herodotus of giant Egyptian statues and by Romans of the bronze Helios at the entrance to the harbor of Rhodes. Figurative sense of "any thing of awesome greatness or vastness" is from 1794.
Helios, the sun, is a god everywhere; there was a scandal when Anaxagoras dared to call him a glowing clod. But the island of Rhodes is almost the only place where Helios enjoys an important cult; ... the largest Greek statue in bronze, the Colossus of Rhodes, is a representation of Helios. [Walter Burkert, "Greek Religion"]
late 14c. as an order of angels, from Late Latin cherub, from Greek cheroub, from Hebrew kerubh (plural kerubhim) "winged angel," which according to Klein is perhaps related to Akkadian karubu "to bless," karibu "one who blesses," an epithet of the bull-colossus. Old English had cerubin, from the Greek plural. But there are other theories:
The cherubim, a common feature of ancient Near Eastern mythology, are not to be confused with the round-cheeked darlings of Renaissance iconography. The root of the terms either means "hybrid" or, by an inversion of consonants, "mount," "steed," and they are winged beasts, probably of awesome aspect, on which the sky god of the old Canaanite myths and of the poetry of Psalms goes riding through the air. [Robert Alter, "The Five Books of Moses," 2004, commentary on Genesis iii.24]
Meaning "a beautiful child" is from 1705. The plural in this sense is cherubs.