"to fasten (a ship) in a particular location by or as by cables, anchors, etc.," late 15c., probably related to Old English mærels "mooring rope," via unrecorded *mærian "to moor," or possibly borrowed from Middle Low German moren or Middle Dutch maren "to moor," from West Germanic *mairojan. Related: Moored, mooring. French amarrer is from Dutch.
<a href="https://www.etymonline.com/word/Moro">Etymology of Moro by etymonline</a>
Harper, D. (n.d.). Etymology of Moro. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/Moro