From the Classical Arabic root ش-ج-ر (sh-j-r), carrying the core sense of branching or spreading out. The root also gives شَجَر (shajar, collective "trees") and مَشَاجِر (mashājir, "thickets/forests"). Cognates appear across Semitic languages, including Aramaic אִילָנָא (ilānā) sharing the branching-spread concept, and the root is attested in the earliest Arabic poetry (pre-Islamic jāhilī verse).

Trees hold deep symbolic weight in Arabic culture and Islamic tradition. The Quran references شَجَرَة prominently — most famously الشَّجَرَة المُبَارَكَة (the blessed tree, an olive tree, Surah An-Nur 24:35) and the forbidden tree in Paradise. In daily life, شَجَرَة النَّسَب (family tree) is a common compound meaning "genealogy," making this word essential far beyond its literal botanical sense.