Etymology
Advertisement
irresistance (n.)
1640s, from assimilated form of in- "not, opposite of" (see in- (1)) + resistance.
Related entries & more 
Advertisement
irreplaceable (adj.)
1806, from assimilated form of in- (1) "not, opposite of" + replaceable. Related: Irreplaceably.
Related entries & more 
ir- 
assimilated form of the two Latin prefixes in- "not," or "in" (see in-) before -r-.
Related entries & more 
prostaglandin (n.)

substance found in seminal fluid, 1936, from German (1935); see prostate + gland + chemical suffix -in (2).

Related entries & more 
herein (adv.)
late Old English herinne "in this;" see here + in. Related: Hereinafter.
Related entries & more 
Advertisement
inexpressible (adj.)

1620s, from in- (1) "not" + expressible (see express (v.)). Inexpressibles "trousers" is from 1790. Related: Inexpressibly.

I have retain'd the word BREECHES, as they are known by no other name amongst country folk.--The change from vulgarity to refinement, in cities and towns, has introduced other appellations; there they are generally called SMALL CLOTHES, but some ladies of high rank and extreme delicacy call them INEXPRESSIBLES. [footnote in "Poems Miscellaneous and Humorous," by Edward Nairne, Canterbury, 1791]

Inexpressibles is the earliest recorded and thus seems to have begotten the trend: Unmentionables (1806); indispensibles (1820); ineffables (1823); unutterables (1826); innominables (1827); and inexplicables (1829) followed.

Related entries & more 
impersuadable (adj.)
1763, from assimilated form of in- (1) "not, opposite of" + persuadable. [Earliest date in OED 2nd ed. print is a typo.]
Related entries & more 
heparin (n.)

substance found in the liver, lungs and other tissues, 1918, from Greek hēpar "liver" (see hepatitis) + -in (2).

Related entries & more 
irredeemable (adj.)
c. 1600, from assimilated form of in- (1) "not, opposite of" + redeemable. Related: Irredeemably.
Related entries & more 
irreducible (adj.)
1530s, from assimilated form of in- (1) "not, opposite of" + reducible. Related: Irreducibly; irreducibility.
Related entries & more 

Page 46