innermost

The word 'innermost' is a transparent superlative formation from the Old English comparative adjective 'inner'. The base 'inne', meaning "inside," originates from Proto-Germanic inn, related to the adverb inna. The superlative suffix '-most' descends from the Old English '-mest', itself a fusion of the superlative suffix '-ma' and the common suffix '-est'. Thus, the literal construction "inner-most" logically evolved to denote the extreme degree of being within, extending metaphorically to describe one's most private feelings or thoughts. This straightforward compounding within the Germanic linguistic tradition efficiently creates a term for the farthest interior point, both physically and psychologically.

Structure: inner + most - inner (Old English: innera, comparative of inne meaning "inside"; functional role: adjective base meaning "situated within") - most (Old English: -mest, superlative suffix; functional role: suffix forming the superlative degree of adjectives)