Morphological contiguity domains are pockets of natural language grammar in which non-contiguous formal isomorphism is prohibited, yielding so-called *ABA distributions. These domains have shown great initial promise as a possible diagnostic for syntactic hierarchical structure, and have been observed in the morphosyntax of pronouns, case, number, gender, tense, possessives, negation, inter multissima alia. This study argues that *ABA domains are heterogeneous in aetiology (i.e., how they emerge diachronically) and derivation (i.e., how they are generated synchronically). Specifically, it identifies two additional lexico-grammatical categories in which the *ABA effect is active: honorifics and kinship. Chapter 2 describes the honorific system of Japanese (Japonic, Japan) which contrasts three levels of social deixis: neutral, honorific (referent-exalting), and humilific (speaker- or ingroup-humbling). Chapter 3 introduces the novel Honorific-Humilific Generalisation, under which a suppletive verb that contrasts all three levels must demonstrate co-suppletion of the honorific and humilific forms. Crucially, this *ABA configuration is demonstrated to pattern with the literature on comparative suppletion. Special attention is paid to the importance of differentiating suppletion from registral alternation, the significant interspeaker variation in the use of honorifics, and the pitfalls of using casual inspection to map transparent containment to underlying structure. Chapter 4 pursues two distinct but overlapping goals. First, it argues that kinship terms are decomposable into abstract morphological features, and that the postsyntactic manipulation of these features suffice to generate all six kinship typologies of traditional anthropology. It reframes the First Fundamental Law of Kinship---in which cross and nuclear terms cannot syncretise to the exclusion of parallel terms---as an *ABA effect that patterns with the literature on case co-lexicalisation. Second, it argues that the Principles of Generational Cyclicity and Agnatic Kinship active in Lower Arrernte (Pama-Nyungan, Northern Territory) work together to instantiate an *ABA domain that results not from syntactic hierarchical containment, but from the manner in which certain kintactic features must always co-occur as triggers of suppletion. It emerges from this crosstheoretic, crossdomanial, and crosslinguistic investigation that although individual contiguity domains can be grouped into natural classes with one another, their space of potential variation is so vast that a surface *ABA distribution alone cannot be an unambiguous diagnostic of a particular kind of underlying structure. Rather, each domain should be studied on its own terms, as each touches upon different components of the human language faculty, to include the modularity of grammar, the featural decomposition of morphosyntactic categories, and the presence of constraints on linguistic form not recapitulated by constraints on cognition.