great achievement
忇 centers on a great achievement or accomplishment, often implying significant effort or merit.
忇 combines 忄 (heart/mind) with 力 (strength/effort), suggesting a mental or heartfelt effort leading to great achievement. The exact historical development is uncertain.
The heart 忄 puts in great effort 力, resulting in a great achievement.
For ロク, imagine a great achievement being recorded in a log book: log -> ロク, and the heart's effort is written down.