An Etymological Dictionary of Astronomy and Astrophysics

To send out → energy, such as → heat or → light, in the form of → rays or → waves.

Etymology (EN): From L. radiat(us), p.p. of radiare “to shine, to beam”

• -ate verbal suffix.

Etymology (PE): Tâbidan, variants tâftan “to shine,” tafsidan “to become hot;” Mid.Pers. tâftan “to heat, burn, shine;” taftan “to become hot;” Parthian t’b “to shine;”
Av. tāp-, taf- “to warm up, heat,” tafsat “became hot,” tāpaiieiti “to create warmth;” cf. Skt. tap- “to heat, be/become hot; to spoil, injure, damage; to suffer,” tapati “burns;” L. tepere “to be warm,” tepidus “warm;” PIE base *tep- “to be warm.”