The most famous reformer of Estonian, Johannes Aavik (1880–1973), used creations ex nihilo (cf. ‘free constructions’, Tauli 1977), along with other sources of lexical enrichment such as derivations, compositions and loanwords (often from Finnish; cf. Saareste and Raun 1965: 76). In Aavik’s dictionary (1921), which lists approximately 4000 words, there are many words which were (allegedly) created ex nihilo, many of which are in common use today. Examples are
Is there an answer to this question (If it cannot be answered, say "unanswerable"): Of all of Estonian's language reformers who is the most well known?
Johannes Aavik