I don't know the exact constitution of the distributions, but there's a difference between a dividend distribution (dividends paid out by the stocks that the ETF holds) and a capital gain distribution (the net realized capital gain that the fund has at the end of the fiscal year, typically paid for the quarter ending December)
ETFs sometimes have their 'dividend yield' reported differently by different quote providers. For instance. on Yahoo!, VEA is indicated as having a yield of 5.31% (or an annualized dividend of $1.75). It all depends on which particular dividends the quote provider is using as an 'annualized' basis - some simply take one quarterly dividend and multiply by 4; others take the trailing 12 months; while others might use different methods and try to only include the distributions from dividends and exclude capital gains distributions.
But at any rate, companies outside of the US are more likely to make irregular or non-quarterly dividend distributions (some annually or semi-annually...others, whatever/whenever the board declares them), and the amounts of the dividends can change substantially, compared to the average US dividend paying company, which might be relatively more consistent. As such, the dividend distributions from ETFs/Mutual Funds that hold foreign companies can have drastically varying dividend amounts from one quarter to the next. And then when you throw in possible capital gain distributions as well, it can really change by a large amount.
On a side note - many foreign countries impose a foreign tax on the dividends that you receive through mutual funds and ETFs. While some funds distribute more foreign dividends (and withhold more foreign tax) than others, it can be worth it if a foreign stock ETF position is large enough to sell it in a tax-advantage account and then buy it in your taxable account. Because of the issue of foreign taxes, I typically hold all of my foreign stock-derived holdings in my taxable accounts, so I can use the foreign tax credit on Form 1040.
However, if you think the tax savings from no capital gains from higher growth in foreign stocks will more than offset losing out on the foreign tax credit, then you would be better off holding them in a tax advantage account.