An Etymological Dictionary of Astronomy and Astrophysics

An area on the surface of the → Moon that appears darker and smoother than its surroundings, once thought to be seas, now known to be lava-flooded basins; plural maria.

Etymology (EN): L. mare “sea,” plural form maria, because
Galileo thought the dark featureless areas on the Moon were bodies of water.

Etymology (PE): Daryânemâ literally “looking like a sea,” from daryâ “sea” (Mid.Pers. daryâp variant zrah; O.Pers. drayah-; Av. zrayah- “sea;” cf. Skt. jráyas- “expanse, space, flat surface”)

• nemâ “looking, showing,” present stem of nemudan “to show, display” (Mid.Pers. nimūdan, nimây- “to show,” from O.Pers./Av. ni- “down; into,” → ni-, + māy- “to measure,” → display.