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Most of the professionals at this business address say they have "clients," a word which used to mean a lower-class denizen living under the protection (or patronage) of a patrician (or upper-class denizen), until English lawyers began referring to their customers by the term in the 1600s, according to the Online Etymology Dictionary. So, a client was someone who was patronized.
The psychiatrists here still do business with patients, which could mean long-suffering people who embody the virtue of patience, the same reference informs us.
I say customer (meaning "person with whom one has dealings") or I use the word visitor or student or associate, depending upon the nature of the transaction at hand.
I am happy to report that it has been over a year since I have heard the word "consumer" being substituted for "client" (usually to refer to the customers of mental-health professionals or institutions) because it sounds more respectable, to some.
As a free-market enthusiast, I do not hear any pejorative connotations reverberating around the word customer. But by "free-market" I do NOT mean today's heartless, high-tech, government-subsidized, state-regulated pseudo-capitalism.
One mental-health paraprofessional informed me that "participant" is the more respectful and egalitarian term now favored, yet reacted to the possibility of being referred to as "one of my participants" with visible and audible dismay. On property management gigs, I have used the words "tenant" and "resident" instead of customer, intending no disrespect.
Working as an airport ramp agent (years ago), I noticed that the even the words "passenger" -- or "ramper" -- could develop some pretty...ah, well, never-mind.
I opine that word connotations emerge and resonate and build up or break down inevitably during common usage (intentionally and unintentionally), through the songs and dances of everyday tones, gestures and expressions. Meanings and nuances generate and re-generate as psyches and souls interact, thinly or thickly disguised by attitudes.
And attitudes can be changed on purpose, I remember happily.