This paper explores the linguistic properties of a discourse variant of the temporal adverb ʔelħi:n, used in Haili Dialect of Najdi Arabic (HA). Maintaining the characteristic of co-occurring clause-initially, and examining lexical/discoursal articulated structures, ʔelħi:n has developed a conventionalized discourse use, turning its morphology into a discourse particle that expresses a degree of speaker’s attitude. ʔelħi:n has undergone a process of grammaticalisation, with morphosyntactic consequence: changing its phrasal status to a head one. Evidence supporting this direction derives from intervention effects (Rizzi, 2006)- ʔelħi:n inhabits movement of head-items in syntax. The immediate consequence of this morphosyntactic change has direct impact on the syntax of ʔelħi:n: occurring clause-initially and its phonology: being unable to bear high tone, unlike its temporal adverb counterpart. Implementing cartographic mechanisms, Rizzi’s (1997) Split CP System, and holding to observations that inherently focused material wh-phrase leɪʃ ‘why’ merges in a position c-commanded by ʔelħi:n, it is established that the discourse instance of ʔelħi:n first merges at a discourse head, instantiating a discourse projection, PrtP, whence it semantically wide-scopes the propositional-TP. Constituents preceding ʔelħi:n are then argued to move and remerge at some Spec of a discourse phrase, C-TopP (Frascarelli & Hinterhölzl, 2007). Mapping the CP-layer of HA, the PrtP headed by ʔelħi:n maintains a rigid order in syntax with respect to CP-items, which makes a possible, initial mapping to the left periphery of HA, calling for scrutiny of more structure.