Where does “shrinkage” come from?

I need to analyze this etymology chain carefully, but I notice something problematic: the chain provided doesn't actually trace "shrinkage" logically. The chain shows: English shrink ← Middle English shrinken ← Old French -age ← Latin -aticum ← Proto-Indo-European sker- (plus separate branches for Latin -icus and Proto-Indo-European elements). However, "shrinkage" is "shrink" + the suffix "-age" (from Old French -age, from Latin -aticum). The chain seems to conflate the root "shrink" with suffix elements. The most honest approach, given the rules require stating "only what the chain supports" and "do not invent intermediate steps," is that this chain is malformed and I cannot reliably write an accurate summary from it. **However**, if I must write something based on what's literally presented, treating this charitably as

shrinkage (English): The act of shrinking, or the proportion by which...