in the slightest. At all, in the smallest degree. These terms are nearly always used in a negative context. For example, I don't care in the least what you do with the money, or It doesn't matter in the slightest whether or not you attend.
[ c. 1600
They may also be put as not in the least or
not in the slightest, as in I am not in the least worried about the outcome, or The heat doesn't bother me in the slightest.
In the least dates from about 1600; in the slightest has been used in the sense of “emphatically unimportant or trifling” since the late 1500s.