too:  Too is historically the same word as to, but the two were not differentiated orthographically until the 16th century. The sense ‘also’ comes from the notion of addition implicit in putting something ‘to’ something else; and ‘addition’ led on to ‘excess’. => to
"in addition, in excess," late Old English, stressed variant of Old English preposition to "in the direction of, furthermore" (see to). The spelling with -oo is from late 16c. Use after a verb, for emphasis (as in did, too!) is attested from 1914. German zu unites the senses of English to and too. Slang too-too "excessive in social elegance" first recorded 1881. Too much is from 1530s as "more than can be endured;" sense of "excellent" first recorded 1937 in jazz slang.