The word 'thickening' is a transparent English formation built upon the ancient Germanic root for density or viscosity. The core adjective 'thick' (Old English þicce) provides the foundational sense of a close-packed or semi-solid consistency. The addition of the verb-forming suffix '-en' transforms this quality into an action, meaning "to make or become thick." Finally, the gerund or noun-forming suffix '-ing' converts this action into a result or substance, yielding the modern abstract and concrete meanings. This logical, layered construction exemplifies how English can generate precise technical and culinary terminology from its native Germanic stock through systematic suffixation.

Structure: thick (dense) + en (verb suffix) + ing (noun suffix) - thick: From Old English þicce (dense, viscous, numerous), of Proto-Germanic origin. Functions as the core adjective/root. - en: A verb-forming suffix from Old English -nian, used to form verbs meaning "to become or make something have the quality of" the root. - ing: A noun-forming suffix from Old English -ung, -ing, used to form nouns denoting a material, result, or process.