Tickle

I balanced a few stones and from the recesses of my mind came the word 'tickle',  to describe something precarious. I had to confirm it.

Searching online was not very useful but fortunately I possess the complete Oxford English Dictionary (1933 edition) in 13 hefty volumes. Discovering obscure and archaic words in these tomes saw my parents through many a long dark wartime evening in the Welsh hills. 

Now, Volume T-U tells me that the adjective tickle, meaning 
In unstable equilibrium, easily upset or overthrown, insecure, tottering; nicely poised; delicate, sensitive
was noted (even then) as a dialect word no longer in general use. The first example recorded was in Foxe's Book of Martyrs of 1583:
A stoole which stood vpon a bolster of a bed, so tickle that any manne or beeste might not touch it so little, but it was ready to fall.


Exactly!