user315: In English as far as I know, pawns were once not pieces. A player had eight pieces and eight pawns which, together, totaled 16 chessmen.
When did this usage change? Why?
And (if you happen to know) how is it in the other major chess languages, like French, German and Russian?

user8201: As you do, I have the impression that the usage has changed within a lifetime, but I can’t be more precise than that. 
I tend to use the generic “unit” as do many problemists. For non-pawns I use the term “officer”, but I am not sure if that includes the king. I am sure I slip into using the word “pieces” often but these days it’s a synonym for “unit”.

user3819: As you ask for German, we make the distinction as in your question:
Figur chess piece
Stein chessman
Bauer pawn

We also distinguish between
Leichtfigur light piece (knight or bishop)

and
Schwerfigur heavy piece (rook or queen)


user-1: The terms are a bit loose. To quote from Wikipedia:

In chess, the word "piece" has three meanings, depending on the context.
1) It may mean any of the physical pieces of the set, including the pawns. When used this way, "piece" is synonymous with "chessman" (Hooper & Whyld 1992:307) or simply "man" (Hooper & Whyld 1987:200).
2) In play, the term is usually used to exclude pawns, referring only to a queen, rook, bishop, knight, or king. In this context, the pieces can be broken down into three groups: major pieces (queen and rook), minor pieces (bishop and knight), and the king (Brace 1977:220).
3) In phrases such as "winning a piece", "losing a piece" or "sacrificing a piece", it refers only to a bishop or knight. The queen, rook, and pawn are specified by name in these cases, for example, "winning a queen", "losing a rook", or "sacrificing a pawn" (Just & Burg 2003:5)

Source: Wikipedia, emphasis is mine.
From the same article, the term pieces to include pawns has been noted since the late 1980's. Speculating, it may be that commentators did not see the need to distinguish between the terms pieces and men, hence coming into common use. For example, Josh Waitzkin's tutorials in Chessmaster, first made in the 1990's, use the term pieces instead of men. I've seen terminology become more lax over time, e.g. pieces being 'killed' instead of 'captured'.
As for other languages, I am unable to say I'm afraid.

315: <p>In English as far as I know, <em>pawns</em> were once not <em>pieces.</em> A player had eight pieces and eight pawns which, together, totaled 16 <em>chessmen.</em></p>

<p>When did this usage change? Why?</p>

<p>And (if you happen to know) how is it in the other major chess languages, like French, German and Russian?</p>
 8201: <p>As you do, I have the impression that the usage has changed within a lifetime, but I can’t be more precise than that. </p>

<p>I tend to use the generic “unit” as do many problemists. For non-pawns I use the term “officer”, but I am not sure if that includes the king. I am sure I slip into using the word “pieces” often but these days it’s a synonym for “unit”.</p>
 3819: <p>As you ask for German, we make the distinction as in your question:</p>

<pre><code>Figur chess piece
Stein chessman
Bauer pawn
</code></pre>

<p>We also distinguish between</p>

<pre><code>Leichtfigur light piece (knight or bishop)
</code></pre>

<p>and</p>

<pre><code>Schwerfigur heavy piece (rook or queen)
</code></pre>
 -1: <p>The terms are a bit loose. To quote from Wikipedia:</p>

<blockquote>
  <p>In chess, the word "piece" has three meanings, depending on the context.</p>
  
  <p>1) <strong>It may mean any of the physical pieces of the set, including the pawns. When used this way, "piece" is synonymous with "chessman"</strong> (Hooper &amp; Whyld 1992:307) or simply "man" (Hooper &amp; Whyld 1987:200).</p>
  
  <p>2) In play, the term is usually used to exclude pawns, referring only to a queen, rook, bishop, knight, or king. In this context, the pieces can be broken down into three groups: major pieces (queen and rook), minor pieces (bishop and knight), and the king (Brace 1977:220).</p>
  
  <p>3) In phrases such as "winning a piece", "losing a piece" or "sacrificing a piece", it refers only to a bishop or knight. The queen, rook, and pawn are specified by name in these cases, for example, "winning a queen", "losing a rook", or "sacrificing a pawn" (Just &amp; Burg 2003:5)</p>
</blockquote>

<p>Source: <a href="https://en.wikipedia.org/wiki/Chess_piece" rel="noreferrer">Wikipedia</a>, emphasis is mine.</p>

<p>From the same article, the term pieces to include pawns has been noted since the late 1980's. Speculating, it may be that commentators did not see the need to distinguish between the terms pieces and men, hence coming into common use. For example, Josh Waitzkin's tutorials in Chessmaster, first made in the 1990's, use the term pieces instead of men. I've seen terminology become more lax over time, e.g. pieces being 'killed' instead of 'captured'.</p>

<p>As for other languages, I am unable to say I'm afraid.</p>
