cripple
蹇 centers on physical impairment that makes walking difficult: a crippled or lame state. The given meaning 'cripple' captures this core idea of hindered movement.
蹇 combines 足 (foot) with a phonetic component that also suggests difficulty or obstruction. The character expresses lameness or crippled movement through the foot radical and the idea of being hindered.
The bottom 足 is a foot, and the top looks like a roof with something blocking the way. Picture a foot trapped under a heavy roof, making the person lame and unable to walk properly.
For ケン, imagine Ken, a man with a crippled foot, struggling to walk: Ken -> ケン, and his lameness is shown by the 足 under the obstructing top.