In Germany, Silke is not only a diminutive form for Celia, but also for Cäcilia.Also, this name is used in The Netherlands as well, where it is a unisex name (rare for men, but in the top 1000 for women). In the case of female bearers, it is most often a diminutive for Celia and Cecilia - but also a diminutive of Sil, which in itself is a *short form* of Cecilia (at least in the case of women). [noted -ed]For men, this name is a diminutive of the mostly Frisian name Sil - please see Sil in the Submitted Names Database for more information.
I would pronounce it like the word silk. If you say it silk-eh it sounds too much like silky, which is far too cutesy to be an actual name. I quite like this name, but it's the sort of name I would use for a character in a story, and not for myself or my kid (if I ever had one).