In Japanese, it was originally recorded in the Nara Period as a verb *samorapu ("to watch, to keep watch, to observe, to be on the lookout for something; to serve, to attend"), which is believed to be derived from the frequentative form (*morapu 守らふ) of the verb moru (守る, "to watch, to guard, to be on the lookout; to keep, to protect, to take care of, to be in charge of, to have as one's ward").
What did 'samorapu' mean?
to watch, to keep watch, to observe, to be on the lookout for something; to serve, to attend