Green’s Dictionary of Slang

1. an absconder; one who has run away.

1865

Leaves from Diary of Celebrated Burglar 10/2: When I got to the place where we had left our look-out, lo! and behold, he was non est, he was a ‘namaser’.

2. something that has vanished, e.g. one’s money.

1865

Leaves from Diary of Celebrated Burglar 87/1: Now look at our [...] sugar, it’s almost a ‘namaser,’ and at this rate we’ll be cleaned out in less than two months.