-erei

Etymology
From, from. The suffix first became productive in German to designate workshops pertaining to occupation names ending in, such as from. These cases are more properly analyzed as derivations in from the occupation name. Later on, began to be freely attached to verb stems, autonomously from agent nouns. Compare e.g. above with  derived directly from. Similar developments took place in 🇨🇬 and, to a lesser degree, 🇨🇬.

Usage notes

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

Etymology
From -er- +.
 * -er- is the reduced form of the Italian infinitive endings and.
 * stems from hĕbui / (h)ĕ(bu)i, from classical, first-person singular perfect of.

The Italian conditional mood stems from a Vulgar Latin periphrastic verb form consisting of infinitive + perfect of habere. Example: Italian stems from  + hĕbui.

Suffix

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