Etymology
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-ia 
word-forming element in names of countries, diseases, and flowers, from Latin and Greek -ia, noun ending, in Greek especially used in forming abstract nouns (typically of feminine gender); see -a (1). The classical suffix in its usual evolution (via French -ie) comes to Modern English as -y (as in familia/family, also -logy, -graphy). Compare -cy.

In paraphernalia, Mammalia, regalia, etc. it represents Latin or Greek -a (see -a (2)), plural suffix of nouns in -ium (Latin) or -ion (Greek), with formative or euphonic -i-.
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-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 compare whitester "one who bleaches cloth;" kempster (c. 1400; Halliwell has it as kembster) "woman who cleans wool." Chaucer ("Merchant's Tale") has chidester "an angry woman." In Modern English, the suffix has been productive in forming derivative nouns (gamester,roadster, punster, rodster "angler," etc.; the 17c. had scoldster).

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