the.com/slack

means Loose, not taut — and by extension, room to breathe: extra material, reduced effort, or forgiveness for falling short.

from From Old English 'sleac,' meaning slow, lazy, or loose, itself from a very old Germanic root tied to looseness and slackening. The rope sense (slack as the loose part of a line) and the moral sense (slack as laziness) grew from the same root side by side for centuries — so 'cut me some slack' and 'pick up the slack' are really the same old word tugging in opposite directions.