The unreasonable fear that there is a spider with the personality of Piers Morgan somewhere.

From Greek "αποβάθρα" (Pier), "αράχνη" (spider) and English suffix -phobia. Origin not quite reconstructible, might have been invented while half-asleep and listening to the news, on which both Piers Morgan and spiders were mentioned.

The ability to conjure snowfall by the mere mention of the word "Snow".

From Ancient Greek χιών (khiṓn, “snow”) + Via Latin, from Ancient Greek γένεσις (génesis). The simplex genesis as a common noun (as opposed to Genesis, the name of the biblical book) from the late 16th century. As an English suffix from the mid 17th century (attested in epigenesis and palingenesis). Influenced by French -génésie and German -genese and productive in scientific vocabulary from the 19th century.

The systematic study and documentation of places, structures, objects and technologies that have outlived their original purpose.

From Greek "εγκατάλειψη" (enkatáleipsi, abandonment), combined with the English suffix "-ics", denoting a field of study.

A Welsh concept of longing, grief, or nostalgia for home — a home which may never have existed or to which you cannot return.

Welsh: a combination of homesickness, grief, and incompleteness.

The eerie, forlorn atmosphere of a place that is usually bustling with people but is now empty and quiet.

Coined by John Koenig. From Greek keno- (empty) + -opsia (seeing).

The state of being infatuated with another person, characterized by intrusive thinking, acute longing, and an intense sensitivity to the other person's actions.

Coined by Dorothy Tennov in Love and Limerence (1979).

More honest than 'infatuation'. It names the cognitive dimension — the intrusion — that infatuation papers over.

The well-founded awareness of one’s own subject-matter competence; the condition of genuinely knowing the shit one is talking about.

From Greek σκῶρ (“dung, excrement”), genitive “σκατός”, and “γιγνώσκειν” (to know, to understand)

The realization that each passerby has a life as vivid and complex as one's own — populated with their own ambitions, friends, routines, worries, and inherited craziness.

Coined by John Koenig, The Dictionary of Obscure Sorrows.

This word did not exist before 2012. It describes a feeling that presumably did.

The strange wistfulness of used bookstores — the sense of accumulated lives, of all the readers who came before, now gone.

Coined by John Koenig. From vellum + ichor (the ethereal fluid in the veins of the gods).