marl (n.) Look up marl at
"clayey soil used for fertilizer," late 14c., from Old French marle (Modern French marne), from Late Latin marglia, diminutive of Latin marga "marl," which is said by Pliny to be a Gaulish word, but modern Celtic cognates are considered to be borrowed from English or French. As a verb by late 14c. Medieval Latin margila is the source of Dutch mergel, German Mergel.