We'll gather lilacs in the spring again
And walk together down a shady lane
Until our hearts have learned to sing again
When you come home once more…
My fellow gardner sent me a photo – is this lilac? It smells lovely – I thought yes but uploaded it to Name This Plant, Microsoft's visual search on Bing, and it came back with Syringa. But a little more digging revealed that is indeed lilac, which is one of about a dozen plant species in the Syringa genus. It originates in the Balkan and the Greek name is paschalia, to do with Easter; pascal is derived from pascha = passover.
The name lilac ultimately stems from Persian nil = blue, which has a variant form nilak, and it has reached us via French < Spanish < Arabic. This made me think of the colour eau-de-nil ("water of the Nile"); could there be a connection.
Well perhaps. The Romans and Greeks called it Nilus and Νιελος, but beyond that the source is very uncertain. However, one possible root that's been suggested is indeed nil, see https://en.wikipedia.org/wiki/Nile#Etymology_and_names