The Slavic languages practically do not have native words containing /f/; this sound, which did not exist in Proto-Indo-European, arose in Greek and Latin from PIE *bʰ (which yielded Slavic /b/), in some instances in Latin represented historical th-fronting, and was derived from Proto-Indo-European *dʰ, and in the Germanic languages from PIE *p (which remained unchanged in Slavic). The letter ф is, therefore, almost exclusively found in words of foreign origin, especially Greek (from ph and sometimes from th), Latin, French, German, English, and Turkic.
Few native Slavic words with this letter (in different languages) are examples of onomatopoeia (like Russian verbs фукать, фыркать etc.) or reflect sporadic pronunciation shifts, for example:
from пв/pv/: Serbian уфати 'to hope' (cf. Church Slavonic уповати 'to hope')
from хв/xv/: Macedonian сфати '(he) understands' (cf. Church Slavonic схватити 'to take, to catch')
from х/x/: Russian toponymФили 'Fili' (from хилый 'sickly')