not sure what "Nicknames describe mental and physical characteristics complain clothes etceteras" means ?

Moore I think has it a little better where he states both were purely Manx names but does throw in the possibility of a different derivation for Kneen

KANEEN, contracted from Mac Cianain, 'Cianan's son,' (Cianan is a diminutive of Cian, which is itself a diminutive of ci, 'to weep.')

' CIANAN, Bishop of Doimhliag died,' A.D. 488.*
Compare (Irish) KEENAN (Gaelic) MAC KINNON.

KYNYNE [1422], KENEEN [1666], KENEN [1676], CANEEN [1729], KANEEN [1740], KENAN [1783].

A purely Manx name. it is almost confined to the parishes of Andreas and Jurby. Andreas (vc), Jurby (c), elsewhere (u).

* Four Mast., Vol. I., P. 153.

KNEEN, probably also a contraction of Mac Cianain. In our early documents it seems to be confused with NEVYN or NEVYNE. Andrew John NEVYN is one of the 24 Keys in 1417, while Jenkin M'NYNE in 1429 is as called Jenkine MAC NEVYNE in 1430. If it is a corruption of NEVYN, which is common in Scotland at the present day in the form NIVEN, it will have quite a different origin : from (Gaelic) Naomh, 'a saint.'

It is a purely Manx name.

MAC NYNE [1429], KNEENE [1504], KNEEN [1598].
Bride (vc), Ballaugh, Marown, Andreas, Lezayre, German, Santon, Rushen (c), elsewhere (u).
(see www.manxnotebook.com/manxnb/v05p020.htm)

Interested in a family motto - though obviously any family can adopt one, though Manx ones are rare, are you possibly confusing with a Scottish Niven which linkage your page seems to deny ?