Definition from Wiktionary, the free dictionary
Etymology 1 
First attested in 1598.
Alternative forms 
- A worker in unmortared stone; a stonemason who has not served an apprenticeship.
- (freemasonry) A person who attempts to pass himself off as a Freemason without having experienced the rituals or going through the degrees.
- (slang) A sneak; an inquisitive or prying person.
- (in attributive use) uninitiated, outside, “profane”
Supporting references for [[#Etymology 1|cowan¹]]
Etymology 2 
First attested in 1722; perhaps from the Scottish Gaelic cobhan (“coffer”, “box”, “ark”).
cowan (plural cowans)
† Cowan ¹. Sc. Obs. rare — ¹. [? a. Gaelic cobhan coffer, box, ark.] A fishing-boat. [¶] 1722 Wodrow Hist. Church Sc. II. 535 The Earl..resolved to man out..thirty large cowans or fisher-boats.
” listed on page 1,111 of volume II (C) of A New English Dictionary on Historical Principles [first edition, 1893]
- “ ” listed in the Oxford English Dictionary [second edition, 1989]
From the Breton kaouenn (“owl”).
cowan f (plural cowannes)
- (ornithology) owl (bird)