in May and June 1798 Arnot appeared 19 times in Godwin's diary, lastly on 13.6.1798 ppc (pour prendre conge, a leavetaking), From 9.4.1799 to 17.3.1801 there were 17 mentions of letters to and from Arnot or his manuscripts and journals, also in this period there were four mentions of Capt Arnot (15.12.1799 to 30.12.1799) and on 12.6.1800 mrs Arnot & Lucy call. Then from 3.11.1802 to 15.12.1802 Arnot appeared 15 times and again from 13.6.1803 to 12.8.1804 he appeared 40 times, most of these were calls. On 20.7.1805 seek Dickins (pro Arnot). Then from 4.8.1810 to 30.12.1811 Godwin wrote to Arnot 6 times. On 21.6.1813 Arnot, surgeon at tea. On 23.10.1815 and 3.11.1815 D Arnot calls and on 6.11.1815 D Arnot commences, and from 13.11.1815 to 29.11.1815 Arnot appeared 5 times, 3 of them associated with Fairly. On 18.7.1826 Arnot (Calcutta) calls. Then on 6.2.1830 Arnot at David Uwins', on 14.3.1831 Arnot at John Martin's and on 20.6.1831 Arnot at Crump's. Finally between 22.2.1836 and 13.3.1836 Arnot calls four times.
For simplicity I suggest that all the Arnots up to 1805 referred to John Arnot, Godwin's 'disciple' and traveller in Europe and his family, while those in 1810, 1811 and 1815 referred to another Arnot, a bookseller. The surgeon of 1813 and all entries after 1826 may have been other Arnots. John Arnot was born 30.11.1776 son of Hugo Arnot DNB 1749-1846. Captain Arnot was his older brother Hugo Robert born 18.7.1773 and died 1838, of the Grenadier Guards. It was presumably his Address to the British Nation "the production of a staunch Whig" that was reviewed in the Gents Mag in April 1812. John & Hugo both have person records in the GD website, where you can find their letters in Abinger Ms listed on the bibliography page. Mrs Arnot of 12.6.1800 was their mother Margaret nee Bennet who married Hugo Arnot 8.7.1770. Lucy of 12.6.1800 must refer to their sister Margaret born 12.9.1774 who married Samuel Fyler (his will PCC 1825 barrister) in 1796, Godwin's letter to her Bodleian Abinger c55 f60-1 and c22 f141-2 referred to the call of 12.6.1800. She may have been called Lucy becuase of having the same name as her mother or Godwin may have got the name wrong. In one of John Arnot's letters to Godwin from Europe, the only siblings he felt some affection for were his oldest sister Christian born 3.4.1771 who married Peter Reid (MD Edinburgh 1804) on 23.7.1801, and a sister Jane. This may have referred to his youngest sister Jean Benet born 21.3.1784 but I'm not sure if she survived infancy, otherwise it may have meant his younger sister Lilias born 22.9.1779 who married Asbury Dickens of Philadelphia on 31.10.1803 who was presumably the Dickins mentioned in Godwin's dairy 4 times in 1805, the last time "(pro Arnot)". What later became of John Arnot I have not discovered, it is not impossible that some of the later Arnots in the diary referred to him. In J Arnott's The House of Arnott (1918), which mentions all the above siblings except Jean Benet and also a younger brother Laurence 1781-1813 a Major in the Army killed in action, it is said of John Arnot he was "believed to have engaged in a duel and fled to the continent", probably a garbled family version of Arnot's adventures in Europe.
Godwin's first surviving letter to John Fairly in Ediburgh (Abinger c10 f85-6) dated 15.5.1809 referred to Mr Arnot as a bookseller in Edinburgh and make it clear that Godwin was unsure if Fairly had mentioned Godwin's identity to Arnot. This suggests that Godwin and Arnot had not met (or perhaps that Godwin was unsure if it was the same Arnot or the same family). Godwin had first met Fairly in London in February 1809 but didn't record meeting an Arnot after 12.8.1804 until Arnot, surgeon in 1813 and then D Arnot in 1815. It seems probable that the 5 Arnot entries in November 1815, three of them associated with Fairly, belonged to the same person as the 3 D Arnot entries just before them. David Gale Arnot was born 17.6.1791 at Urchfont, Wiltshire, son of David & Hannah (nee Hames) whose marriage was announced in the Gents Mag July 1790. He may have been apprenticed to a surgeon in Somerset in 1808 and he died 11.4.1842 at Wyfold Court, Peppard, Oxon having married Catherine Kemble 24.8.1830 at Lewisham St Mary, his will PCC 1842 bookseller of Ave Maria Lane. No record of his having been a bookseller in Edinburgh nor can I find him in London directories and he seems to have been born and died in reasonably comfortable circumstances. Edinburgh directories listed a William Arnot & Co booksellers 38 Princes St 1807, 1811, 9 Merchant St 1818-9, 50 South Bridge Bible Depository 1824. D Arnot who "commenced" on 6.11.1815 may have been his son or relative starting an apprenticeship or employment with Godwin