The Collaborative International Dictionary of English v.0.48:

Mester \Mes"ter\, n. [Obs.]
   See Mister, a trade.
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The Collaborative International Dictionary of English v.0.48:

Mister \Mis"ter\, n. [OF. mistier trade, office, ministry, need,
   F. m['e]tier trade, fr. L. ministerium service, office,
   ministry. See Ministry, Mystery trade.] [Written also
   mester.]
   1. A trade, art, or occupation. [Obs.]
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            In youth he learned had a good mester. --Chaucer.
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   2. Manner; kind; sort. [Obs.] --Spenser.
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            But telleth me what mester men ye be. --Chaucer.
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   3. Need; necessity. [Obs.] --Rom. of R.
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