plural thalami, 1753, "the receptacle of a flower," Modern Latin, from Latin thalamus "inner chamber, sleeping room" (hence, figuratively, "marriage, wedlock"), from Greek thalamos "inner chamber, bedroom," related to thalame "den, lair," tholos "vault, vaulted building." Used in English since 1756 of a part of the forebrain where a nerve appears to originate.