PWS

*gann-, *gann-at- - garden (Kogan 2015: 208)

If the Geez word gannat ‘garden’ is autochthonous, the present lexeme cannot be considered a specific feature of PCS. A reflex of *gann- ‘garden’ is probably to be seen in Amh. gännänä ‘to flourish, to grow well (plants, trees), to be abundant (vegetation)’. Relatively broad presence of the reflexes in ESA obviates the necessity of postulating a “Northern” borrowing in Ethiopian (and an Aramaic borrowing in Arabic) (Kogan 2015: 208-209)

PS
*gnn/gny/gnˀ - to enclose, to protect, to shelter (DRS 147‒149; Kogan 2015: 209)

Akkadian
gannu - garden (CAD G 41, AHw. 280)
Var. gannatu.
An Aramaism (Abraham–Sokoloff 2011:30).
Ugaritic
gn - garden, orchard (DUL 302)
Hebrew
gan - garden (HALOT 198)
Hebrew
gannā - garden (HALOT 199)
Syriac
gantā - garden (LSyr. 122, SL 250)
Arabic
ǯannat- - garden (Lane 463)
According to a widespread opinion, Arb. ǯannat- was borrowed from Aramaic (сf. Nöldeke 1910:42, CDG 199, with references).
Sabaic
t-gn - garden, orchard (SD 50)
Sabaic
gnt - garden, orchard (SD 50)
Minaean
gnt - jardin (garden) (LM 36)
Qatabanian
gnn - garden (LIQ 39)
Qatabanian
gnn - to cultivate (LIQ 39)
Geez
gannat - garden (CDG 199)
a loanword?
Mehri
gənnēt - paradise (ML 121)
borrowed from Arabic
Jibbali
gɛnt - paradise (JL 76)
borrowed from Arabic