appended to the stem of a verb, this suffix yields a verbal noun; it is similar in function to the Dutch suffix -ing
köken: From Proto-Germanic *-þiz. The -s- is the result of a wrong segmentation of stem and suffix of a noun in cases where the stem of the noun ended with -s-. For example: a word like Dutch vorst (“frost”) could be interpreted as vors+t or as vor+st. This suffix existed already in Gothic (𐌰𐌽𐍃𐍄𐍃 (ansts), from *𐌿𐌽𐌽𐌰𐌽 (*unnan)).
köken: First attested in the Seokbo sangjeol (釋譜詳節 / 석보상절), 1447, as Middle Korean ᄀᆞ자ᇰ〮 (Yale: kòcáng). Original meaning: "very, extremely". Superlative meaning ("most") from sixteenth century onward. Displaced previous superlative adverbs 안〮직 (Yale: áncìk), ᄆᆞᆺ〮 (Yale: mós).
köken: Probably a lexicalization of i, an early variant of the demonstrative pronoun e /ez (“this”). Possibly formed with -g /-ig (terminative suffix) (compare míg and possibly leg-) and -en (adverb-forming suffix) (compare hogyan, ígyen). In its original sense, it was probably used to express emphasis. First attested in 1266. According to Johanson (2004), borrowed from a Turkic particle egen ~ igen…