The process that gives rise to the inferior olivary nucleus. This process pertains to the initial formation of a structure from unspecified parts. The inferior olivary nucleus is a capsule-shaped structure in the ventral medulla located just lateral and dorsal to the medullary pyramids. Neurons in the inferior olivary nucleus are the source of climbing fiber input to the cerebellar cortex; these neurons have been implicated in various functions, such as learning and timing of movements. [ GOC:jid http://openisbn.com/search.php?q=0838580343&isbn=1/ GOC:dgh http://purl.obolibrary.org/obo/go/references/0000021 GOC:cls GOC:dph ]