11 And he shall go forth, suffering pains and afflictions and temptations of every kind; and this that the word might be fulfilled which saith he will take upon him the pains and the sicknesses of his people.His boss happened to be nearby and pointed out that the root word of infirmities is firm, which supported my argument that another word for infirmities could be weaknesses. If you're in-firm, you're not steady. You're weak. (Which can definitely be a result or symptom of sickness, but does not merely refer to being ill.)
12 And he will take upon him death, that he may loose the bands of death which bind his people; and he will take upon him their infirmities, that his bowels may be filled with mercy, according to the flesh, that he may know according to the flesh how to succor his people according to their infirmities. (Alma 7:11-12)
Then I went on to say that it doesn't even necessarily mean physical weaknesses, but all those parts of us that are less than steady. Our bad habits, our personality flaws, all our deviations from the ideal can be infirmities. (The intern agreed with me [indirectly - she wasn't involved in this particular conversation], saying that as a perfectionist she knows so well how infirm she is and how what she needs to work on are unique to her -- unique to her and Christ through his Atonement.)
This ties in well with the idea of enabling grace. Christ's grace that enables us to act in power, to overcome our challenges both external and internal.
27 And if men come unto me I will show unto them their weakness. I give unto men weakness that they may be humble; and my grace is sufficient for all men that humble themselves before me; for if they humble themselves before me, and have faith in me, then will I make weak things become strong unto them. (Ether 12:27)All we need to do is come unto Christ. He will open our eyes to our infirmities and give us the strength to overcome.