The story
From Ancient Greek θηλή (thēlḗ, “nipple”) + -arche. By surface analysis, thel- + -arche.
Etymology from Wiktionary, CC BY-SA 4.0.
thelarche
Today it means: The first stage of postnatal breast development, usually occurring at the beginning of puberty in girls, in which a firm, tender lump develops under the centre of the nipple. Full definition →