Known in his lifetime as a medical and theological writer, he was also responsible in his capacity as physician to Michael Faraday for the term "electrode", a fact not known until well into the 20th century.
His father was rector of the parish, and died before Nicoll was two years old; his mother was Ann, daughter of George Hatch of Windsor.
[2] In 1806 Nicoll became a student at St George's Hospital, and in 1809 received the diploma of membership of the College of Surgeons of England.
[2] Nicoll began to write aon medicine in the London Medical Repository in 1819; his first separate publication, Tentamen Nosologicum had already appeared there, a general classification of diseases based upon their symptoms.
General Elements of Pathology’ appeared in 1820, and in 1821 Practical Remarks on the Disordered States of the Cerebral Structures in Infants.
This was first read before an association of physicians in Ireland on 6 December 1819; he proposed that erethism of the cranial brain is due to impressions on the anticerebral extremities of nerves, but this theory went beyond his actual observations.