all
僉 centers on the idea of all or everyone together, as a collective whole.
僉 is thought to combine 亼 (a gathering) with 从 (people) and 吅 (mouths), suggesting many people speaking together, hence 'all'. The exact historical development is uncertain.
The top 亼 looks like a roof gathering people (从) with many mouths (吅) underneath, all speaking at once — everyone together.
For セン, imagine a scene where all the people are gathered around a cent (coin) on the ground: cent -> セン, and everyone wants a piece.