-ing1

1.
a suffix of nouns formed from verbs, expressing the action of the verb or its result, product, material, etc. (the art of building; a new building; cotton wadding). It is also used to form nouns from words other than verbs (offing; shirting). Verbal nouns ending in -ing are often used attributively (the printing trade) and in forming compounds (drinking song). In some compounds (sewing machine), the first element might reasonably be regarded as the participial adjective, -ing2, the compound thus meaning “a machine that sews,” but it is commonly taken as a verbal noun, the compound being explained as “a machine for sewing.”.
Compare -ing2 .
Origin
Middle English; Old English -ing, -ung

-ing2

1.
a suffix forming the present participle of verbs (walking; thinking), such participles being often used as participial adjectives: warring factions.
Compare -ing1 .
Origin
Middle English -ing, -inge; the variant -in (usually represented in spelling as -inʾ) continues Middle English -inde, -ende, Old English -ende
Pronunciation note
The common suffix -ing2 can be pronounced in modern English as either
[‐ing] /‐ɪŋ/ (Show IPA)
or
[‐in] /‐ɪn/
with either the velar nasal consonant
[ng] /ŋ/
symbolized in IPA as [ŋ], or the alveolar nasal consonant
[n] /n/
symbolized in IPA as [n]. The
[‐in] /‐ɪn/
pronunciation therefore reflects the use of one nasal as against another and not, as is popularly supposed, “dropping the g, ” since no actual g -sound is involved.
Many speakers use both pronunciations, depending on the speed of utterance and the relative formality of the occasion, with
[‐ing] /‐ɪŋ/
considered the more formal variant. For some educated speakers, especially in the southern United States and Britain,
[‐in] /‐ɪn/
is in fact the more common pronunciation, while for other educated speakers,
[‐ing] /‐ɪŋ/
is common in virtually all circumstances. In response to correction from perceived authorities, many American speakers who would ordinarily use
[‐in] /‐ɪn/
at least some of the time make a conscious effort to say
[‐ing] /‐ɪŋ/
even in informal circumstances.

-ing3

1.
a native English suffix meaning “one belonging to,” “of the kind of,” “one descended from,” and sometimes having a diminutive force, formerly used in the formation of nouns: farthing; shilling; bunting; gelding; whiting.
Compare -ling1 .
Origin
Middle English, Old English -ing, cognate with Old Norse -ingr, -ungr, Gothic -ings
British Dictionary definitions for -ing

-ing1

suffix
1.
(from verbs) the action of, process of, result of, or something connected with the verb: coming, meeting, a wedding, winnings
2.
(from other nouns) something used in, consisting of, involving, etc: tubing, soldiering
3.
(from other parts of speech): an outing
Word Origin
Old English -ing, -ung

-ing2

suffix
1.
forming the present participle of verbs: walking, believing
2.
forming participial adjectives: a growing boy, a sinking ship
3.
forming adjectives not derived from verbs: swashbuckling
Word Origin
Middle English -ing, -inde, from Old English -ende

-ing3

suffix
1.
a person or thing having a certain quality or being of a certain kind: sweeting, whiting
Word Origin
Old English -ing; related to Old Norse -ingr
Word Origin and History for -ing

suffix attached to verbs to mean their action, result, product, material, etc., from Old English -ing, -ung, from Proto-Germanic *unga (cf. Old Norse -ing, Dutch -ing, German -ung). Originally used to form nouns from verbs and to denote completed or habitual action. Its use has been greatly expanded in Middle and Modern English.

suffix used form the present participle of verbs, from Old English -ende (cf. German -end, Gothic -and, Sanskrit -ant, Greek -on, Latin -ans). It evolved into -ing in 13c.-14c.