男 is made of two ideograms: 田 “field” and 力 “strength” (this latter character could have evolved from a pictogram of a plough). In old times, ploughing (and working the field in general) was a man’s job. In most of the historical forms of 男, the “field” is positioned either on top or to the left of the “plough”. Also, in an alternative character 㽖 the “field” is on the left side. The “plough” part looks a bit like lower-case letter n which helps me to remember that nán is a “man” which starts with n.