The origins of this phrase are uncertain, but it has been observed in print since at least 1889, and likely was around well before that. The potentially related phrase "to a tittle" is found in a 1607 play, The Woman Hater by Francis Beaumont and John Fletcher ("I'll quote him to a tittle"). The T in the phrase to a T is likely the first letter of a word, with tittle being the most likely source.
- Other theories with little evidence point to golf tees, for their small size; this may have at least influenced the alternate form to a tee. Some speculate a relationship with T-square, a measuring device introduced around the turn of the century. Others claim the expression refers to the correct completion of the letter t by crossing it.