From Middle English, from Old English -sum (“-some, same as”). Akin to Old Frisian -sum (“-some”), Old High German -sam (“-some”), Old Norse -samr (“-some”), Gothic -𐍃𐌰𐌼𐍃 (-sams), -𐍃𐌰𐌼𐌰 (-sama). Cognate with Albanian -shëm (“-some”). More at same.
Middle English from a specialized note of Old English sum (“some, one”) coming after a genitive plural (e.g. hē wæs fēowertiga sum --"he was one of forty", literally "he was forties' some[one]"; sixa sum --"one of six, sixsome").
- Used to form a word indicating a group with a certain small number of members