the mind > attention and judgement > enquiry > investigation, inspection > secret observation, spying > procedures used in spying > surveillance [verb (transitive)] > investigate as private detective (2)
Sherlock1913
to engage in detective work; to investigate (something), to make deductions about.
Sherlock Holmes1922
transitive to make deductions about, to assess, to deduce (cf. Sherlockv. at Sherlock, n. derivatives).