(ii) Shen (8127) - from 8150; a tooth (as sharp); specifically (for 8143) ivory; figuratively, a cliff:
Shanan (8150) - a primitive root; to point (transitive or intransitive); intensively, to pierce; figuratively, to inculcate: - also used for 'to teach diligently'!
Pure, sharp (cutting edge)
Same Hebrew used as for Teeth.
(iii) Teaching others with purity and sharpness in the Spirit.
(iv) (a) 5:4; 7:4