-sch

From Middle Dutch -sch.

-sch

1. archaic form of -s (“suffix forming adjectives”)

• Occasionally used in deliberately archaising language; e.g. a product marketed to appeal to a sense of nostalgia may use a spelling such as Hollandsch instead of Hollands.
• In some cases this archaising usage extends even to words ending in -s today which historically did not end in -sch at all. For example, some university sororities may include the word damesch (from dames, plural of dame (“lady”)): a completely made-up archaism, as the plural marker -s historically was never spelled -sch.

• -'sch

Contraction of -isch.

• IPA^(key): /ʃ/, [ʃ]

-sch

1. A suffix attached to names to produce eponymous adjectives: -ean, -ian, 's

   die Boolesche/boolesche Algebra ― Boolean algebra

• Words in -sch inflect like normal adjectives.
• While the name generally remains capitalised with the spelling -'sch, it may alternatively be lowercased without the apostrophe (provided that the adjective is neither nominalised nor part of a fixed term).

From Old Dutch -isc, from Proto-Germanic *-iskaz.

-sch

1. -ish, -an; Used to form adjectives of origin.

• -sc

• Dutch: -s (older -sch)