accomplished, reach, arrive, attain
達 centers on reaching a destination or a goal: arriving somewhere, attaining a state, or becoming accomplished. The idea of reaching extends naturally to the pluralizing suffix たち, which marks a group that has been gathered or arrived at.
達 combines 辶 (movement) with a phonetic element that historically contributed the sound and the idea of reaching or passing through. The inner component is related to 幸, but the exact historical development is uncertain.
The movement radical 辶 suggests a path, and the inner part looks like a stack of 土 (earth) and 羊 (sheep). Picture a sheep climbing over mounds of earth to finally reach its destination.
For タツ, imagine reaching the top of a tall tatsu (竜, dragon) statue: tatsu -> タツ, and you have accomplished the climb.
pluralizing suffix (esp. for people and animals; formerly honorific)
friend; companion
achievement; attainment; accomplishment; realization
development; growth
official notice; notification
reaching; attaining; arrival
delivery
supply; provision; raising; procurement
elegance; dandyism; sophistication; having style
master; expert
transmission (e.g. news, chemical signals, electricity); communication; delivery; conveyance; transfer; relay; propagation; conduction
to reach; to get to; to arrive at
improvement (e.g. in skill, ability); advance; progress
purveyor (to the Imperial Household, etc.)
notification; official notice; directive (e.g. from higher to lower levels of the administration)
daruma; tumbling doll; round, red-painted good-luck doll in the shape of Bodhidharma, with a blank eye to be completed when a person's wish is granted
in good health; healthy; well; fit; robust; strong
deliverer; deliveryman; delivery person
express; special delivery
leader; pioneer; precursor; senior figure