meaning: 辱=辰+寸, why? What does it mean?
Han Dynasty linguist Hsu Shen's explanation in Shuo-wen Chieh-Tzu:


  【清·陳昌治刻本·說文解字】辱：恥也。从寸在辰下。失耕時，於封畺上戮之也。辰者，農之時也。故房星為辰，田候也。
  
  【清·段玉裁·說文解字注】恥也。心部曰。恥，辱也。此之謂轉注。儀禮注曰。以白造緇曰辱。从寸在辰下。會意。寸者，法度也。而蜀切。三部。失耕時。故从辰。於封畺上戮之也。故从寸。辰者，農之時也。故房星爲辰。說从辰之意。


According to him, 辰 refers to date/time, i.e. for farming; and 寸 refers to laws and the judicial system. This explanation draws upon the fact that ancient China, especially under the Chou Dynasty was heavily focused on agriculture. Because various stages of farming (planting, harvesting, etc) was time critical, those who messed up the dates were disgraced.

Thus 辱 comes from the judicial humiliation 寸 for missing the correct times for farming 辰. This meaning of "to humiliate" came into currency during the mid-late Chou Dynasty. In the bronze script, this character had a radical 言, denoting the verbal nature of the humiliation.

However, it might not have been the original meaning for that character.

By this I mean we are discussing the ancestor of the ancestor of the clerical script character 辱. When traced all the way back to oracle bone scripts, the character 辱 (or rather, its ancestor) meant "to weed". Modern scholars have argued that this came from a farming tool (seashell) 辰 being used by the right hand 又. The radical 又 later mutated into 寸 in the seal script.

This original bone script meaning developed into the clerical script character 耨. Also, that is where the explanation cited in the question came from. I would guess that at some point, @user3306356's source mixed up the two different lineages.