when sadness is heavy upon our soul

The word sadiron landed in my inbox today as my daily mail from A Word a Day. The meaning of the word is

noun: a heavy flatiron pointed at both ends and having a detachable handle. And the etymology is 'From sad (obsolete senses of the word: heavy, solid) + iron Earliest documented use: 1759.

When I'm sad I do feel heavy, in every limb, so I can understand how this word came to have such a meaning.

The Online Etymology Dictionary says:

sad (adj.) Old English saed "sated, full, having had one's fill (of food, drink, fighting, etc.), weary of," [and gives further detail in the full description of this word's history.] Sense development passed through the meaning "heavy, ponderous" (i.e. "full" mentally or physically), and "weary, tired of" before emerging c. 1300 as "unhappy." An alternative course would be through the common Middle English sense of "steadfast, firmly established, fixed" (as in sad-ware "tough pewter vessels") and "serious" to "grave". In the main modern sense, it replaced Old English unrot, negative of rot "cheerful, glad." 

I wonder what other utensils are sad? Surely it's not just the irons and pewter vessels.

At Words, Words, Words, the writer of the blog writes more about this history, and ends with this:

But one thing that people don't know about sadness is that it is silent. You can't spot it from a mile away, it could be right next to you as you read this. But it is not the be all and end all, you can overcome sadness, but first you have to be able to see it.

I agree. We need to keep our radar scanning for sad people around us, and also to check inside ourselves to see if we are dealing with our own sadness.