Use after a verb, for emphasis (as in did, too!) is attested from 1914. 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. German zu unites the senses of English to and too.
late Old English ofer-done "carried to excess, immoderate, too much;" see overdo. Of meat, etc., "cooked too much," from 1680s.
also over-strung, 1767 of musical instruments, "with strings too tense;" 1801, of persons, "too sensitively organized," from over- + strung. In the figurative extension, the notion is the one in the colloquial expression wound too tight.As a type of pianowith string sets crossing each other obliquely, by 1860.