-erei

From Middle High German [Term?], from Old French -erie. The suffix first became productive in German to designate workshops pertaining to occupation names ending in -er, such as Bäckerei (“bakery”) from Bäcker (“baker”). These cases are more properly analyzed as derivations in -ei from the occupation name. Later on, -erei began to be freely attached to verb stems, autonomously from agent nouns. Compare e.g. Bäckerei above with Backerei (“baking”) derived directly from backen (“to bake”). Similar developments took place in Dutch -erij and, to a lesser degree, English -ery.

• IPA^(key): /əˈʁaɪ̯/

-erei f (genitive -erei, plural -ereien)

1. Used to form verbal nouns, which often have an informal and/or negative overtone.

   warten (“to wait”) — Warterei (“[lengthy] waiting”)

   singen (“to sing”) — Singerei (“[unpleasant] singing”)

• This suffix is of virtually unlimited productivity in colloquial German.
• Verbs whose stems end in -er- or -el- use the simple suffix -ei instead:

quengeln (“to whine”) — Quengelei (“whining”)

• ge-

• -ei

From -er- + -ei.

• -er- is the reduced form of the Italian infinitive endings -are and -ere.
• -ei stems from Vulgar Latin hĕbui / (h)ĕ(bu)i, from classical Latin habuī, first-person singular perfect of habeō.[1]

The Italian conditional mood stems from a Vulgar Latin periphrastic verb form consisting of infinitive + perfect of habere. Example: Italian loderei (“I would praise”) stems from Vulgar Latin laudare + hĕbui.[1]

-erei

1. Used with a stem to form the first-person singular conditional of regular -are and -ere verbs.

See also Italian grammar, section Conditional mood in the English Wikipedia.