With later on shortening with the vowel. The meaning "a divide of land" (sense two), attested earlier in watershed (18th century) seems to become an outgrowth of before Bodily senses from the phrase, as "the Portion of a person's hair" or "a passageway amongst the threads of the warp on https://4x8shed75319.ktwiki.com/863349/indicators_on_sidemate_you_should_know