mjhjmtu

In the following sentence what does 'Custom' actually mean?

Three times a day for many months I had witnessed this performance, but custom had not reconciled my mind to it.

I know custom means usual practice and tradition but it doesn't seem to mean that here.

Reference:
This sentence is taken from the first chapter, second paragraph of Sherlock Holmes: Sign of Four.

'Custom', as you indicated, is often used to talk about traditional practices or behaviours. For example:

• It is a wide-spread custom in most Christian countries to exchange gifts on or around Christmas Day.




• It is a custom in many countries for businessmen to shake hands when they meet.

However, 'custom' can also be used to describe the unique habits or behaviours of a single person or a small group of people. For example:

• It was his custom to bring home flowers for his wife at the end of each week.




• Joe and his friends went surfing at the weekend, as was their custom.

In your case, the author has witnessed a particular performance 'three times a day for many months'. So, it is reasonable enough for us to say that it was the author's custom to witness this performance three times a day. However, in spite of this custom, the author was unable to reconcile his mind to it.

The meaning of custom here is:

[Merriam-Webster]

1 c : repeated practice

// Custom makes all things easy.

The meaning of reconciled in this sentence is unclear as there is no context and there are several possibilities that could fit:

[Merriam-Webster]

1 b : SETTLE, RESOLVE

// reconcile differences
2 : to make consistent or congruous

// reconcile an ideal with reality
3 : to cause to submit to or accept something unpleasant

// was reconciled to hardship

So, there is something about the performance that doesn't make sense (either internal to the performance or in its relationship to reality) or something about it that is unpleasant to witness.

In any case, you can paraphrase the sentence in this way:

Three times a day for many months I had witnessed this performance, but no matter how many times I saw it, I couldn't (accept, understand, or enjoy) what I saw.

In this case, 'custom' means familiarity. If you do something often enough, regularly enough, even if that thing is initially traumatising or shocking or disgusting or concerning (like watching your friend shoot up drugs), you 'get used' to it - you become desensitised.

Imagine if you had a new roommate who, say, cut their toenails every night in front of the telly, you might find it absolutely disgusting, and be certain that no one could convince you otherwise. But fast forward 3 months and you might not even notice it any more. And the housemate would certainly find it a bit strange if you suddenly started yelling at them about it, after 3 months of silence.

In the story of your quote, Watson has watched Holmes shoot up drugs every night for three months, yet it still annoys him as much as the first time. This surprises Watson because in any other situation he would have either been spurred to speak up and protest / make a comment by now, or alternatively, just tolerate it as part of life with Holmes.

Reading the full context of this sentence (or even just the next sentence) immediately clears up any doubt and may be of interest to the other valiant answer-ers.

FULL CONTEXT: (from https://ebooks.adelaide.edu.au/d/doyle/arthur_conan/d75si/chap01.html )

Sherlock Holmes took his bottle from the corner of the mantelpiece,
and his hypodermic syringe from its neat morocco case. With his long,
white, nervous fingers he adjusted the delicate needle and rolled back
his left shirtcuff. For some little time his eyes rested thoughtfully
upon the sinewy forearm and wrist, all dotted and scarred with
innumerable puncture-marks. Finally, he thrust the sharp point home,
pressed down the tiny piston, and sank back into the velvet-lined
armchair with a long sigh of satisfaction.

Three times a day for many months I had witnessed this performance, but custom had not reconciled my mind to it. On the contrary, from
day to day I had become more irritable at the sight, and my
conscience swelled nightly within me at the thought that I had lacked
the courage to protest. Again and again I had registered a vow that I
should deliver my soul upon the subject; but there was that in the
cool, nonchalant air of my companion which made him the last man with
whom one would care to take anything approaching to a liberty. His
great powers, his masterly manner, and the experience which I had had
of his many extraordinary qualities, all made me diffident and
backward in crossing him.

The straight forward meaning in this sentence is "repetition" so: "but repetition had not reconciled my mind to it".

But by using custom the writer also manages to convey ideas about it being the "custom" of the people that are being witnessed and hints that this was something that the witness could not become "accustomed" to.