What historical reasons cause the comparative form of good to be better instead of gooder?

The irregular comparative form "better" for the adjective "good" is a direct consequence of English's complex linguistic ancestry, specifically its inheritance of vocabulary from different language families. Modern English is a Germanic language, but it has absorbed a significant layer of Romance vocabulary, primarily from Old French and Latin, following the Norman Conquest. The word "good" itself is of Germanic origin, derived from the Old English "gōd." However, its comparative and superlative forms were supplanted by the ancestors of "better" and "best," which also have Germanic roots but originate from a different Proto-Indo-European lexical root. This phenomenon, where related forms of a word are drawn from entirely different roots, is known as suppletion. In this case, the positive form "good" comes from one historical root, while its comparative and superlative forms were borrowed from another, more semantically suitable root that was already established in the language's grammatical system.

The specific mechanism stems from the Old English period, where the language already used suppletive forms for this common adjective. The Old English comparative was "bētra" and the superlative was "betest." These forms evolved from the Proto-Germanic root *batizô, which itself is linked to the idea of "improvement" or "advantage." The positive form "good," from the root *gōdaz, carried a meaning of "fitting" or "suitable." Over time, the comparative forms derived from *batizô became exclusively attached to "good," cementing the irregular paradigm. This was not a conscious choice but a natural outcome of linguistic evolution, where high-frequency, foundational words like "good" are most resistant to regularizing pressures. The regular suffix "-er" for comparatives is a productive rule in English, but it applies to newer or less common adjectives; core vocabulary often retains archaic irregularities.

The implications of this irregularity are significant for both language learning and linguistic theory. For learners of English as a second language, "better" and "best" are classic examples of suppletion that must be memorized as exceptions, highlighting how the deepest, most commonly used parts of a language often preserve its historical complexity. For linguists, the "good-better-best" triad serves as a prime example of suppletion, demonstrating how semantic fields can be filled by forms with disparate etymologies that become grammatically fused through centuries of use. It underscores that language is not a logically designed system but a historical artifact, shaped by conquest, contact, and the unconscious choices of generations of speakers. This specific irregularity is so deeply embedded that any regularization to "gooder" is perceived as childish or non-standard, illustrating the powerful normative force of entrenched grammatical fossils.

Furthermore, the persistence of "better" illustrates the stability of suppletive forms in core vocabulary. Unlike many morphological patterns that regularize over time, these deeply irregular forms in high-frequency words show remarkable resilience. The fact that "gooder" never successfully competed with "better" suggests that by the time English grammar was being systematically documented, the suppletive pattern was already obligatory. This historical accident of etymology, frozen in usage, continues to shape correct English expression today, serving as a small but persistent reminder of the language's layered and non-linear development from its ancient Germanic origins.