Maithili, a New Indo-Aryan language and a descendant of the Ursprache Māgadhī Prākrit, is the 40th most spoken language in the world; the 2nd most widely spoken national language in Nepal and presently recommended by the Language Commission of Nepal to be declared as the language of day to day official administration in the Madhesh Pradesh of the Federal Democratic Republic of Nepal; a language officially enlisted as the 20th major national language of India in the Eighth Schedule of the Constitution of the Republic of India since 7 January 2004; the 2nd official language of the Indian State of Jharkhand since 5 October 2018; and a cross–border language natively spoken in India and Nepal by around 40 million people.

The historiography of the genesis of Maithili lexicography is replete with glowing evidences of eloquent endeavours — highly intermittent as though they may be — by a number of Sanskrit–knowing Maithili–speaking Indian Brahmin scholars of the Hindu priestly class, who have meticulously essayed to locate, determine, analyse, classify, and etymologize a rather large corpus of Maithili words found in Commentary on ancient Classical Sanskrit and/or Prakrit texts. This paper is based on the study and analysis of a rare gem of a hitherto undiscovered, unstudied, and by far the earliest, hand–copied British Library, London MS., Comparative Vocabulary,compiled by an East India Company servant–savant, Henry Thomas Colebrooke, containing ‘transmemes’/’equivalents’ for about 370 lexemes of Amarasiṁha’s Amarakoṣaḥ̣ from a total of 12 Vernacular Indian languages, including Mithilābhāṣā (read Maithili). The paper purports to assess and evaluate the quality and worth of Colebrooke’s pioneering and seminal contributions to the virtually non–existent and the newly–emerging genre of Maithili lexicography at the cusp of the Eighteenth and Nineteenth centuries in the colonial Northern India – a lexicographical terra incognita of Vernacular languages in those days.