Particular characteristics of suffixal complication, which has an articulated dynamic nature, require the application of synchronous and diachronic approaches to their study. Synchronous and diachronic study of complex formants implies the consideration of the previous historical changes when analysing synchronous states, as well as the study of dynamic processes in the word-formational, lexical and semantic subsystems of a language in determinate historical stages of its development. The method of synchronous and diachronic analysis of word-formation models with genetically complex word-formation affixes is presented by the example of the suffix -nits(a) with an object meaning. Synchronous and diachronic analysis of derived words with the suffix -nits(a), which implies the study of systemic relations between the nouns with the suffix -nits(a) in the Old Russian in the different stages of its development, reveals a genetic connection and a historical interaction of the modern Russian word-formation types with the suffixes -nits(a) and -n(ya), which are close semantically and include the derived words with the meaning of container and premises. The suffix -nits(a) with an object meaning is formed in the suffixal complication models “-n(ya) + -its(a)” in the nomina loci group. During its historical development, an extension of the semantic scope of application of the complex formant -nits(a) is observed, and its meaning transcends the boundaries of the names of premises group. The structural and functional evolvement of a new complex formant is empowered both by the peculiarities of nomina loci derivation and by the analogous influence of structurally and semantically close lexical units. The historical development of the suffix -nits(a) results in the following changes in its relations with the suffix -n(ya): the transition from the motivation relations to the relations of co-derivation, the increased productivity of the new complex formant, its prevalence in the competition with the genetically related suffix -n(ya).