toil, slave away, busy
矻 centers on intense, grinding labor: toiling, slaving away, or being constantly busy with hard work.
矻 combines 石 (stone) with 乞, which likely contributes a phonetic element. The stone component may suggest the hardness or grinding nature of the toil.
A stone 石 beside a bent figure 乞: imagine someone bent over a heavy stone, grinding away in endless toil.
For コツ, picture the sound of a stone being chipped away: kotsu kotsu, like the steady rhythm of hard work. Kotsu -> コツ.