thalamus (n.)

"bridal song," 1590s (earlier in nativized form epithalamy, 1580s), from Latin epithalamium, from Greek epithalamion "a bridal song," noun use of adjective meaning "of or for a bridal, nuptial," from epi "at, upon" (see epi-) + thalamos "bridal chamber, inner chamber" (see thalamus). Related: Epithalamic.

before vowels ophthalm-, word-forming element meaning "eye," mostly in plural, "the eyes," from Greek ophthalmos "eye," originally "the seeing," a word of uncertain origin. Perhaps from ōps "eye" (from PIE root *okw- "to see") + a form related to thalamos "inner room, chamber" (see thalamus), giving the whole a sense of "eye and eye socket," but Beekes rejects all this and finds it to be probably Pre-Greek.

"song sung before a wedding, piece written to celebrate a marriage," 1590s, coined as a poem title ("Prothalamion, or a Spousall Verse") by Edmund Spenser (based on epithalamion) from Greek pro "before" (see pro-) + thalamos "bridal chamber" (see thalamus). Sometimes Latinized as prothalamium.