the.com/tad

means A small, deliberately vague amount — more than none, less than you'd have to measure.

from Originally an American colloquialism for a small child — a tadpole's cousin, so to speak, or simply short for 'tadpole' itself, that wriggling baby-frog shape suggesting something small and incomplete. By the 1800s it had hopped from describing little kids to describing little anything: a tad more salt, a tad late. The precise jump from 'small child' to 'small amount' isn't fully documented, but the logic — small thing becomes word for smallness — tracks a very common path in language.