Meaning of -ISH in English
suffix forming adjectives:
1. from nouns, meaning: a having the qualities or characteristics of (boyish). b of the nationality of (Danish).
2 from adjectives, meaning 'somewhat' (thickish).
3 colloq. denoting an approximate age or time of day (fortyish; six-thirtyish).
Etymology: OE -isc 2.
suffix (also -ise) forming verbs (vanish; advertise).
Etymology: from or after F -iss- (in extended stems of verbs in -ir) f. L -isc- incept. suffix
Oxford English vocab. Оксфордский английский словарь. 2012