"a vertebrate which has gills and fins adapting it for living in the water," Old English fisc "fish," from Proto-Germanic *fiskaz (source also of Old Saxon, Old Frisian, Old High German fisc, Old Norse fiskr, Middle Dutch visc, Dutch vis, German Fisch, Gothic fisks), perhaps from PIE root *pisk- "a fish." But Boutkan on phonetic grounds thinks it might be a northwestern Europe substratum word.
Popularly, since Old English, "any animal that lives entirely in the water," hence shellfish, starfish (an early 15c. manuscript has fishes bestiales for "water animals other than fishes"). The plural is fishes, but in a collective sense, or in reference to fish meat as food, the singular fish generally serves for a plural. In reference to the constellation Pisces from late 14c.
Fish (n.) for "person" is from 1750 with a faintly dismissive sense; earlier it was used in reference to a person considered desirable to "catch" (1722). Figurative sense of fish out of water "person in an unfamiliar and awkward situation" attested by 1610s (a fisshe out of the see in the same sense is from mid-15c.). To drink like a fish is from 1744. To have other fish to fry "other objects which invite or require attention" is from 1650s. Fish-eye as a type of lens is from 1961. Fish-and-chips is from 1876; fish-fingers from 1962.
mid-14c., adjective in past participle form from fin.
Old English softe "gently," from the adjective (see soft (adj.)). It is attested from late 13c. as "quietly." As an interjection, "go softly, not so fast," from 1540s.
Old English softe, earlier sefte, "gentle, mild-natured; easeful, comfortable, calm, undisturbed; luxurious," from West Germanic *samfti, from Proto-Germanic *samftijaz "level, even, smooth, gentle, soft" (source also of Old Saxon safti, Old High German semfti, German sanft; and from a variant form with -ch- for -f-, Middle Dutch sachte, Dutch zacht, German sacht), from PIE root *sem- (1) "one; as one, together with" (the source of seem andsame). The etymological sense would be "smooth and agreeable," to the touch, senses, or mind.
From c. 1200 of persons, hearts, etc., "tender, yielding to emotions," also "easily moved or swayed; soft-hearted, sympathetic; docile." It is attested from late 14c. as "indulgent," also "physically feeble; effeminate, easily overcome, lacking manly courage." The meaning "foolish, simple, silly" is attested from 1620s.
It is attested from mid-13c. of material things, "not stiff, not coarse, fine; yielding readily to pressure." Of sounds or voices, "quiet, not loud or harsh," from early 13c. Of words, "mild, restrained; courteous" mid-14c. From late 14c. of wind, rain, etc.
From 1755 of water ("relatively free from mineral salts"), from 1789 of coal (generally meaning bituminous as opposed to anthractic). In reference to drinks, "non-alcoholic" by 1880. Of letters (-c-, -g-, etc.) when pronounced with more sibilance and less plosiveness, 1630s.
In reference to technology, "using natural resources," by 1974, perhaps 1970. Of a science or methods or data, "not subject to experimental verification, not mathematical," c. 1960.
Many phrases simply are contrasts to earlier ones in hard: Soft landing is from 1958 and the U.S. space program; soft rock as a music style is attested from 1969. Soft spot "weak or vulnerable place," literal and figurative, is by 1933, colloquial. The soft sell sales pitch that relies on gentle persuasions is so called by 1955. Soft-shoe as a dancing style is attested from 1927. The photographic soft-focus (adj.), in reference to camera lenses or shots, is from 1917; figurative use of it is by 1961. The softer sex "women collectively" is from 1640s.
mid-13c., "that which is agreeable," from soft (adj.). By 1590s as "the soft part" of anything. In politics it has occasionally since c. 1847 referred to the less extreme faction. The sense of "a fool" is by 1854.
1892, gefüllte Fisch, not a species but a loaf made from various kinds of ground fish and other ingredients; the first word is Yiddish, from German gefüllte "stuffed," from füllen "to fill" (from PIE root *pele- (1) "to fill").