A.T. Robertson Commentary Mark 14:71

"But he began to curse, and to swear, I know not this man of whom ye speak." — Mark 14:71 (ASV)

Curse (αναθεματιζειν). Our word anathema (ανα, θεμα, an offering, then something devoted or a curse). Finally the two meanings were distinguished by αναθημα for offering and αναθεμα for curse. Deissmann has found examples at Megara of αναθεμα in the sense of curse. Hence the distinction observed in the N.T. was already in the Koine. Matthew 26:74 has καταθεματιζειν, which is a απαξ λεγομενον in the N.T., though common in the LXX. This word has the notion of calling down curses on one's self if the thing is not true.