Morphology of mobster, gangster, webster, hipster

Solution 1:

The suffix-ster was originally a feminine suffix but in modern English has been used to form various derivative nouns with no specific gender:

Webster (n.):

• "a weaver," Old English webbestre "a female weaver," from web (q.v.) + fem. suffix -ster. Noah Webster's dictionary first published 1828.

Gangster (n.) :

• "member of a criminal gang," 1896, American English, from gang (n.) in its criminal sense + -ster.

Hipster

• 1941, "one who is hip;" from hip (adj.) + -ster. Meaning "low-rise" in reference to pants or skirt is from 1962; so called because they ride on the hips rather than the waist (see hiphuggers).

-ster

Old English -istre, from Proto-Germanic *-istrijon, feminine agent suffix used as the equivalent of masculine -ere (see -er (1)). Also used in Middle English to form nouns of action (meaning "a person who ...") without regard for gender.

The genderless agent noun use apparently was a broader application of the original feminine suffix, beginning in the north of England, but linguists disagree over whether this indicates female domination of weaving and baking trades, as represented in surnames such as Webster, Baxter, Brewster, etc. (though spinster probably carries an originally female ending). Also whitester "one who bleaches cloth." In Modern English, the suffix has been productive in forming derivative nouns (gamester, punster, etc.). (Etymonline)