Origin: 1535–45; < L
instīgātus ptp. of
instīgāre to goad on, impel, equiv. to
in- in- 2 +
-stīg- goad, prick (akin to
stigma, stick 2 ) +
-ātus -ate 1 
Related forms: in⋅sti⋅gat⋅ing⋅ly, adverb
in⋅sti⋅ga⋅tive, adjective
Synonyms:
1. arouse, provoke. 2. induce, stimulate, encourage, push; initiate, start.