प्र = प् र
प् rope/ limb
र water flow blood liquid
hence
flow (from/to) limb = breath (as opposed to अपान)
leg in water
roped water can mean cleaning water by passing through rope/s
rope+water can mean vines growing in water. Lkely नल in this sense, it means naturally occurring
roped water can refer to pulling water with a rope in this sense it means progressive and ample
limb in water
limb flow
OR
प्र = प + ऋ
Leg superior side - prehensile side of leg
This could mean superior as opposite to inferior side and can mean up side of leg
or it can mean superior as better side and can mean prehensile side of leg. The word emerges when leg used to be prehensile. the inferior side being प्ल.
Because प्लुत mean speed, प्ल refers to non prehensile leg.
रूढ अर्थ
progressive motion
excess/excellence = comes from rope+water sensec
appearance, manifestation = in reflection sense
natural (derived रूढ अर्थ when used as प्रत्यय)
Commentary
प्र in वर्ण/वर्ण-समास Era प्र means vine/rope growing in water. This meaning continues thru वर्ण समास epoch uptoडुकृञ् epoch where it evvolves into its उपसर्ग use.
Hence, as the building block of प्रत्यय, “प्र” means rope/vine growing in water.
As उपसर्ग it takes रूढ अर्थ.