Meaning

noun North American annual plant with usually yellow or orange flowers; grows chiefly on wet rather acid soil

noun perennial herb with branched woody stock and bright yellow flowers

originFrom Middle English celidoine, Old French celidoine, French chélidoine, from Latin chelīdonia, from chelīdonius (“relating to the swallow”), from Ancient Greek χελιδόνιος (khelidónios), χελιδών (khelidṓn). It was traditionally supposed to flower when the swallows appeared, and to perish when they departed.

Etymology from Wiktionary, CC BY-SA 3.0