The Collaborative International Dictionary
Chelidonius
Chelidonius \Chel`i*do"ni*us\, n. [L. (sc. lapillus.)] A small stone taken from the gizzard of a young swallow. -- anciently worn as a medicinal charm.
Wiktionary
chelidonius
n. (context rare English) A stone supposed to be taken from the stomach of a swallow, with purported magical or medicinal properties.