From either 正 (masa)
meaning “exact, precise,” also used as 将, 政 meaning "rule" and 真 meaning "pure, true," or the stem of the verb 勝る/優る (masaru)
meaning "to excel, surpass, exceed; to outweigh," also used as 昌 meaning "prosperous" and 雅 meaning "refinement, elegance."
It can also be written with 2 kanji by combining a ma
kanji, like 真, 満 meaning "full, whole" or 麻 meaning "hemp, flax," and a sa
kanji, such as 砂 meaning "sand" or 佐 meaning "help."
Though it had some usage as a feminine name before the 20th century, nowadays, it is mainly used as a nickname for names (mainly masculine ones) starting with Masa-
, like MASAYOSHI