What is "to strain courtesy"

Strain \Strain\, v. t. [imp. & p. p. Strained; p. pr. & vb. n. Straining.] [OF. estraindre, estreindre, F. ['e]treindre, L. stringere to draw or bind tight; probably akin to Gr. ? a halter, ? that which is squeezwd out, a drop, or perhaps to E. strike. Cf. Strangle, Strike, Constrain, District, Strait, a. Stress, Strict, Stringent.]

1. To draw with force; to extend with great effort; to stretch; as, to strain a rope; to strain the shrouds of a ship; to strain the cords of a musical instrument. ``To strain his fetters with a stricter care.''
   --Dryden.

2. (Mech.) To act upon, in any way, so as to cause change of form or volume, as forces on a beam to bend it.

3. To exert to the utmost; to ply vigorously.

   He sweats, Strains his young nerves.
   --Shak.

   They strain their warbling throats To welcome in the spring.
   --Dryden.

4. To stretch beyond its proper limit; to do violence to, in the matter of intent or meaning; as, to strain the law in order to convict an accused person.

   There can be no other meaning in this expression, however some may pretend to strain it.
   --Swift.

5. To injure by drawing, stretching, or the exertion of force; as, the gale strained the timbers of the ship.

6. To injure in the muscles or joints by causing to make too strong an effort; to harm by overexertion; to sprain; as, to strain a horse by overloading; to strain the wrist; to strain a muscle.

   Prudes decayed about may track, Strain their necks with looking back.
   --Swift.

7. To squeeze; to press closely.

   Evander with a close embrace Strained his departing friend.
   --Dryden.

8. To make uneasy or unnatural; to produce with apparent effort; to force; to constrain.

   He talks and plays with Fatima, but his mirth Is forced and strained.
   --Denham.

   The quality of mercy is not strained.
   --Shak.

9. To urge with importunity; to press; as, to strain a petition or invitation.

   Note, if your lady strain his entertainment.
   --Shak.

10. To press, or cause to pass, through a strainer, as through a screen, a cloth, or some porous substance; to purify, or separate from extraneous or solid matter, by filtration; to filter; as, to strain milk through cloth.

    To strain a point, to make a special effort; especially, to do a degree of violence to some principle or to one's own feelings.

    To strain courtesy, to go beyond what courtesy requires; to insist somewhat too much upon the precedence of others; -- often used ironically.
    --Shak.