Could you please tell me the precise meaning of "secure and inviolate" in this excerpt from the chapter seven of The Great Gatsby, by F. Scott Fitzgerald?
"His wife and his mistress, until an hour ago secure and inviolate, were slipping precipitately from his control."
The sentence to which you refer, from the Great Gatsby, by F. Scott Fitzgerald, is something the narrator, Nick, says about Tom Buchanan.
Chapter seven is a devastating chapter for nearly everyone in this novel, and nearly the entire chapter takes place in the span of one day. Daisy is forced to choose between Gatsby, the man she loves now, and her husband, Tom. Gatsby discovers that Daisy, the woman whom he has worshipped with a kind of romantic idolatry, has fallen from her pedestal--and she chooses Tom over him. This is also the last time Gatsby ever sees Daisy. Nick sees all of the other primary characters at their worst and says he has "had enough of all of them for one day." Tom suffers the worst losses, though it is difficult to feel much sympathy for him.
In her growing boldness, Daisy has invited Gatsby and Nick over for lunch today. Nick is afraid something awful will happen, and it does. It is a strained occasion for everyone but Daisy; she betrays her feelings for Gatsby, perhaps inadvertently, and Tom recognizes it.
Gatsby's eyes floated toward her. "Ah," she cried, "you look so cool." Their eyes met, and they stared together at each other, alone in space. With an effort she glanced down at the table.
"You always look so cool," she repeated.
She had told him that she loved him, and Tom Buchanan saw. He was astounded. His mouth opened a little and he looked at Gatsby and then back at Daisy as if he had just recognized her as someone he knew a long time ago.
Tom immediately agrees with Daisy's suggestion that they go to town, and on the way he, Nick, and Jordan boldly stop for gas at Wilson's Garage, home of Tom's mistress, Myrtle Wilson. Wilson is morose, having just discovered that his wife has been having an affair (though he does not know it is with Tom). He says:
"I've been here too long. I want to get away. My wife and I want to go west."
"Your wife does!" exclaimed Tom, startled.
"She's been talking about it for ten years." He rested for a moment against the pump, shading his eyes. "And now she's going whether she wants to or not. I'm going to get her away."
As Tom drives them away from the garage, Nick makes the observation which contains the sentence you ask about:
There is no confusion like the confusion of a simple mind, and as we drove away Tom was feeling the hot whips of panic. His wife and his mistress, until an hour ago secure and inviolate, were slipping precipitately from his control. Instinct made him step on the accelerator with the double purpose of overtaking Daisy and leaving Wilson behind.
In a matter of moments, literally, Tom has leaned that his wife loves another man and his mistress will be moving away soon. What he thought he had, he no longer has. What was secure, "that which cannot be moved or lost" (according to one definition) is no longer secure. What he thought was inviolate has been violated: it has been disturbed, broken, damaged, and infringed upon. Two things which, in his arrogance and selfishness, he thought he could not lose, have been lost to him--his wife and his mistress.
Myrtle is, of course, lost to him forever; he is able to win Daisy back and, now that Gatsby is dead, will probably keep her because, unlike Tom, Daisy only had one other love and is not out looking for another.