Although Elias Lönnrot did not learn Swedish until he went to school, he mastered it so well that he could use it freely in his private correspondence, his diaries and in his later years as the language of the home. Lönnrot was not opposed to the use of Swedish in Finland, even if he did promote Finnish by substantively broadening its scope.  And wherever language matters took on a political or inflammatory turn, he stayed out of the fray. He was one of the first to speak on behalf of parity for Finnish and Swedish usage: when leaving his professorial post in 1862 he gave a speech to the students in which he took a stand on the language issue, emphasising that two living languages in Finland could only be a blessing for the nation’s education and hence its future.

Lönnrot’s ideas about language lacked the strong puritanical streak so evident in the effusions of many of his contemporaries. In developing specialist vocabulary he avoided loan words, but was favourably disposed towards various ‘calques’, whereby words from other languages were taken as a basis for Finnish words.

His objection to loanwords was that Finnish belonged to another language family than the Indo-European source languages making their contribution to the Finnish 'wordstore'. Instead Lönnrot preferred the idea of enriching the language by exploiting to the full the various dialects and languages close to Finnish. In his correspondence he discoursed at length on the translation of specialist terms in such areas as geography, arithmetic and grammar. A particularly prolific contributor to the cause was the wordsmith Wolmar Schildt-Kilpinen.