This word has developed its meaning over the centuries, from physical state to a particular kind of mental state. Today, the "anger" meaning is the dominant one, but this is never found in Shakespeare. The meaning then was "frame of mind", or now, "temperament". When Aufidius says to Coriolanus, "You keep a constant temper" (Coriolanus, V.ii.90), he does not mean that the latter is always cross. Often there is a clue in the associated adjective: "good temper" (Henry IV Part 2, II.i.79), "feeble temper" (Julius Caesar, I.ii.129), "noble temper" (King John, V.ii.40), "comfortable temper" (Timon of Athens, III.iv.72). A second common meaning was in relation to swords, which all have a "temper", that is a desirable quality or condition: "Between two blades, which bears the better temper", says Warwick (Henry VI Part 1, II.iv.13). Temper for Angelo means "self-control": "Never could the strumpet ... Once stir my temper"
(Measure for Measure, II.ii.185). And when Lear says "Keep me in temper"
(King Lear, I.v.44), he means "keep me stable".