If Alexander Hetherwick had done nothing else, he would be remembered as a pioneer linguist and Bible translator in the Malawi context. To some extent his work on language flowed naturally out of his daily interaction with the people around him. When he went on ulendo (a trip) to ‘Angoniland’ (Ntcheu), for example, he could be in African company and communicating in the vernacular for up to three weeks at a time. Yet the disciplined work of Bible translation and production of other forms of literature often had to be conducted in a quiet hour or two at the end of a busy day or during school holidays when he could sometimes snatch some days for concentrated work. This language work was close to his heart and he frequently lamented his failure to give it the attention he felt it deserved.

Two major languages were spoken in the Blantyre Mission sphere during the 1880s: Mang’anja and Yao. The first missionaries had favoured Yao as the likely lingua franca but by the time Hetherwick arrived Clement Scott had adopted Mang’anja as the primary language at Blantyre. Strategically, however, since the plan was for Hetherwick to establish a new station to the north in a predominantly Yao-speaking area, he decided that this was the language he should learn. At Scott's suggestion he went to stay with John Buchanan, one of the first group of Blantyre missionaries who had become an independent planter. He was by now based at Zomba and had become a fluent Yao speaker. Hetherwick employed what later became known as the ‘immersion method’, devoting two months to daily conversation in a Yao-speaking community. Soon he was being introduced to Yao folklore, thereby becoming ever more skilled in idiomatic expression. By 1885, according to his biographer, he could speak Yao as fluently as English. For Hetherwick, Yao was a most beautiful language – ‘the Italian of the Bantu languages’. He regretted that it was being displaced by Mang’anja as the primary language of the Shire Highlands. ‘I am glad to learn of your intention to do something at Yao,’ he wrote to a European with language-learning aspirations in 1910. ‘It is a very neglected tongue I fear nowadays, but it is by far the finest of the languages hereabout.’